Core/Calendar: Implement different timezone support for ingame calendar

Closes #8390
Closes #29427

(cherry picked from commit b888b1b09f71a8b8b4a9d45c804a1f164fb65ac3)

47 files changed, 1188 insertions, 462 deletions

diff --git a/dep/boost/CMakeLists.txt b/dep/boost/CMakeLists.txt
index 5d0f372594e..845f4ee8edc 100644
--- a/dep/boost/CMakeLists.txt
+++ b/dep/boost/CMakeLists.txt
@@ -29,7 +29,7 @@ else()
   set(BOOST_REQUIRED_VERSION 1.71)
 endif()
 
-find_package(Boost ${BOOST_REQUIRED_VERSION} REQUIRED system filesystem program_options iostreams regex)
+find_package(Boost ${BOOST_REQUIRED_VERSION} REQUIRED system filesystem program_options iostreams regex locale)
 
 if(NOT Boost_FOUND)
   if(NOT DEFINED ENV{BOOST_ROOT} AND NOT DEFINED Boost_DIR AND NOT DEFINED BOOST_ROOT AND NOT DEFINED BOOSTROOT)
diff --git a/sql/base/auth_database.sql b/sql/base/auth_database.sql
index 32724d2ef56..8a82e84f05c 100644
--- a/sql/base/auth_database.sql
+++ b/sql/base/auth_database.sql
@@ -46,6 +46,7 @@ CREATE TABLE `account` (
   `muteby` varchar(50) CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci NOT NULL DEFAULT '',
   `locale` tinyint unsigned NOT NULL DEFAULT '0',
   `os` varchar(4) CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci NOT NULL DEFAULT '',
+  `timezone_offset` smallint NOT NULL DEFAULT '0',
   `recruiter` int unsigned NOT NULL DEFAULT '0',
   `battlenet_account` int unsigned DEFAULT NULL,
   `battlenet_index` tinyint unsigned DEFAULT NULL,
@@ -2759,6 +2760,7 @@ INSERT INTO `updates` VALUES
 ('2023_11_09_01_auth.sql','BC9BC28D41608A78166B5A38F3A7F598FBDB879D','RELEASED','2023-11-09 18:21:59',0),
 ('2023_11_14_00_auth.sql','192D729737C5E3332D7B5B9B7F9DBDD9626D7B98','RELEASED','2023-11-14 11:36:05',0),
 ('2023_11_15_00_auth.sql','DC89EA5C9D799C213B3E6A606F081697ADEF8250','RELEASED','2023-11-15 10:47:53',0),
+('2023_11_21_00_auth.sql','146E5E6EF94C5DB78343372A8FDB32B062B80040','RELEASED','2023-11-21 11:24:11',0),
 ('2023_11_23_00_auth.sql','EC3D1289A07E387BF4D2AC94EEBE3A29483EAD3A','RELEASED','2023-11-23 02:39:18',0);
 /*!40000 ALTER TABLE `updates` ENABLE KEYS */;
 UNLOCK TABLES;
diff --git a/sql/updates/auth/master/2023_11_21_00_auth.sql b/sql/updates/auth/master/2023_11_21_00_auth.sql
new file mode 100644
index 00000000000..1dc190782d7
--- /dev/null
+++ b/sql/updates/auth/master/2023_11_21_00_auth.sql
@@ -0,0 +1 @@
+ALTER TABLE `account` ADD `timezone_offset` smallint NOT NULL DEFAULT '0' AFTER `os`;
diff --git a/src/common/Utilities/Timer.h b/src/common/Time/Timer.h
index e0ecb5b2d13..e0ecb5b2d13 100644
--- a/src/common/Utilities/Timer.h
+++ b/src/common/Time/Timer.h
diff --git a/src/common/Time/Timezone.cpp b/src/common/Time/Timezone.cpp
new file mode 100644
index 00000000000..f7acfe5df5c
--- /dev/null
+++ b/src/common/Time/Timezone.cpp
@@ -0,0 +1,179 @@
+/*
+ * This file is part of the TrinityCore Project. See AUTHORS file for Copyright information
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the
+ * Free Software Foundation; either version 2 of the License, or (at your
+ * option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "Timezone.h"
+#include "Hash.h"
+#include "MapUtils.h"
+#include "Util.h"
+#include <boost/locale/date_time_facet.hpp>
+#include <boost/locale/generator.hpp>
+#include <chrono>
+#include <unordered_map>
+
+namespace
+{
+std::unordered_map<uint32, Minutes, std::identity> InitTimezoneHashDb()
+{
+#if TRINITY_PLATFORM == TRINITY_PLATFORM_WINDOWS
+
+    // Generate our hash db to match values sent in client authentication packets
+    std::unordered_map<uint32, Minutes, std::identity> hashToOffset;
+    std::chrono::system_clock::time_point dummmy;
+    for (std::chrono::time_zone const& zone : std::chrono::get_tzdb().zones)
+    {
+        std::chrono::sys_info sysInfo = zone.get_info(dummmy);
+        Minutes offsetMinutes = std::chrono::duration_cast<Minutes>(sysInfo.offset);
+        std::string offsetStr = Trinity::ToString(offsetMinutes.count());
+        hashToOffset.emplace(Trinity::HashFnv1a(offsetStr), offsetMinutes);
+    }
+
+#else
+    // Pre-generated list of timezone offsets and their hashes for compilers (and their stl implementations) that dont support timezone api yet
+    std::unordered_map<uint32, Minutes, std::identity> hashToOffset =
+    {
+        { 0xAADC2D37u, -720min },
+        { 0x362F107Bu, -690min },
+        { 0x2C44C70Cu, -660min },
+        { 0xB84A209Eu, -640min },
+        { 0xBA3D57D1u, -630min },
+        { 0x4040695Au, -600min },
+        { 0xB65A75D0u, -570min },
+        { 0xC8614DEBu, -540min },
+        { 0x3A68BD26u, -510min },
+        { 0x51E8096Cu, -480min },
+        { 0x4DD8F896u, -420min },
+        { 0x674B7C0Fu, -360min },
+        { 0x633C6B39u, -300min },
+        { 0x0BAD340Au, -240min },
+        { 0x74B25683u, -225min },
+        { 0x09B9FCD7u, -210min },
+        { 0x150C169Bu, -180min },
+        { 0x191B2771u, -120min },
+        { 0xD7D3B14Eu, -60min },
+        { 0x47CE5170u, -44min },
+        { 0x350CA8AFu, 0min },
+        { 0x15E8E23Bu, 60min },
+        { 0x733864AEu, 120min },
+        { 0xF71F9C94u, 180min },
+        { 0xBDE50F54u, 210min },
+        { 0x2BDD6DB9u, 240min },
+        { 0xB1E07F42u, 270min },
+        { 0x454FF132u, 300min },
+        { 0x3F4DA929u, 330min },
+        { 0xD1554AC4u, 360min },
+        { 0xBB667143u, 390min },
+        { 0x9E2B78C9u, 420min },
+        { 0x1C377816u, 450min },
+        { 0x1A4440E3u, 480min },
+        { 0xB49DF789u, 525min },
+        { 0xC3A28C54u, 540min },
+        { 0x35A9FB8Fu, 570min },
+        { 0x889BD751u, 600min },
+        { 0x8CAAE827u, 660min },
+        { 0x7285EE60u, 690min },
+        { 0x1CC2DEF4u, 720min },
+        { 0x89B8FD2Fu, 765min },
+        { 0x98DBA70Eu, 780min },
+        { 0xC59585BBu, 840min }
+    };
+#endif
+
+    return hashToOffset;
+}
+
+std::unordered_map<uint32, Minutes, std::identity> const _timezoneOffsetsByHash = InitTimezoneHashDb();
+
+using ClientSupportedTimezone = std::pair<Minutes, std::string>;
+std::array<ClientSupportedTimezone, 11> const _clientSupportedTimezones =
+{{
+    { -480min, "America/Los_Angeles" },
+    { -420min, "America/Denver" },
+    { -360min, "America/Chicago" },
+    { -300min, "America/New_York" },
+    { -180min, "America/Sao_Paulo" },
+    {    0min, "Etc/UTC" },
+    {   60min, "Europe/Paris" },
+    {  480min, "Asia/Shanghai" },
+    {  480min, "Asia/Taipei" },
+    {  540min, "Asia/Seoul" },
+    {  600min, "Australia/Melbourne" },
+}};
+}
+
+namespace Trinity::Timezone
+{
+Minutes GetOffsetByHash(uint32 hash)
+{
+    if (Minutes const* offset = Containers::MapGetValuePtr(_timezoneOffsetsByHash, hash))
+        return *offset;
+
+    return 0min;
+}
+
+Minutes GetSystemZoneOffsetAt(SystemTimePoint date)
+{
+    Seconds offset;
+#if TRINITY_PLATFORM == TRINITY_PLATFORM_WINDOWS
+    offset = std::chrono::current_zone()->get_info(date).offset;
+#else
+    tm buf = TimeBreakdown(std::chrono::system_clock::to_time_t(date));
+    offset = Seconds(buf.tm_gmtoff);
+#endif
+    return std::chrono::duration_cast<Minutes>(offset);
+}
+
+Minutes GetSystemZoneOffset(bool applyDst /*= true*/)
+{
+    std::chrono::system_clock::time_point date = std::chrono::system_clock::from_time_t(std::time_t(0));
+    if (applyDst)
+        date = std::chrono::system_clock::now();
+
+    return GetSystemZoneOffsetAt(date);
+}
+
+std::string GetSystemZoneName()
+{
+#if TRINITY_PLATFORM == TRINITY_PLATFORM_WINDOWS
+    return std::string(std::chrono::current_zone()->name());
+#else
+    static std::locale calendarLocale = boost::locale::generator().generate("");
+    std::unique_ptr<boost::locale::abstract_calendar> p(std::use_facet<class boost::locale::calendar_facet>(calendarLocale).create_calendar());
+    return p->get_timezone();
+#endif
+}
+
+std::string_view FindClosestClientSupportedTimezone(std::string_view currentTimezone, Minutes currentTimezoneOffset)
+{
+    // try exact match
+    auto itr = std::find_if(_clientSupportedTimezones.begin(), _clientSupportedTimezones.end(), [currentTimezone](ClientSupportedTimezone const& tz)
+    {
+        return tz.second == currentTimezone;
+    });
+    if (itr != _clientSupportedTimezones.end())
+        return itr->second;
+
+    // try closest offset
+    itr = std::min_element(_clientSupportedTimezones.begin(), _clientSupportedTimezones.end(), [currentTimezoneOffset](ClientSupportedTimezone const& left, ClientSupportedTimezone const& right)
+    {
+        Minutes leftDiff = left.first - currentTimezoneOffset;
+        Minutes rightDiff = right.first - currentTimezoneOffset;
+        return std::abs(leftDiff.count()) < std::abs(rightDiff.count());
+    });
+
+    return itr->second;
+}
+}
diff --git a/src/common/Time/Timezone.h b/src/common/Time/Timezone.h
new file mode 100644
index 00000000000..769bf0c5921
--- /dev/null
+++ b/src/common/Time/Timezone.h
@@ -0,0 +1,37 @@
+/*
+ * This file is part of the TrinityCore Project. See AUTHORS file for Copyright information
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the
+ * Free Software Foundation; either version 2 of the License, or (at your
+ * option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef TRINITYCORE_TIMEZONE_H
+#define TRINITYCORE_TIMEZONE_H
+
+#include "Define.h"
+#include "Duration.h"
+
+namespace Trinity::Timezone
+{
+TC_COMMON_API Minutes GetOffsetByHash(uint32 hash);
+
+// Returns the time offset that must be added to UTC time to get localtime
+TC_COMMON_API Minutes GetSystemZoneOffsetAt(SystemTimePoint date);
+TC_COMMON_API Minutes GetSystemZoneOffset(bool applyDst = true);
+
+TC_COMMON_API std::string GetSystemZoneName();
+
+TC_COMMON_API std::string_view FindClosestClientSupportedTimezone(std::string_view currentTimezone, Minutes currentTimezoneOffset);
+}
+
+#endif // TRINITYCORE_TIMEZONE_H
diff --git a/src/common/Utilities/Hash.h b/src/common/Utilities/Hash.h
index b63201bf07a..18f7442fb44 100644
--- a/src/common/Utilities/Hash.h
+++ b/src/common/Utilities/Hash.h
@@ -19,6 +19,7 @@
 #define TrinityCore_Hash_h__
 
 #include <functional>
+#include <string_view>
 #include <utility>
 
 namespace Trinity
@@ -28,6 +29,17 @@ namespace Trinity
     {
         seed ^= std::hash<T>()(val) + 0x9E3779B9 + (seed << 6) + (seed >> 2);
     }
+
+    inline std::uint32_t HashFnv1a(std::string_view data)
+    {
+        std::uint32_t hash = 0x811C9DC5u;
+        for (char c : data)
+        {
+            hash ^= c;
+            hash *= 0x1000193u;
+        }
+        return hash;
+    }
 }
 
  //! Hash implementation for std::pair to allow using pairs in unordered_set or as key for unordered_map
diff --git a/src/common/Utilities/Util.cpp b/src/common/Utilities/Util.cpp
index ac97e724902..d852ed655a0 100644
--- a/src/common/Utilities/Util.cpp
+++ b/src/common/Utilities/Util.cpp
@@ -58,9 +58,20 @@ std::vector<std::string_view> Trinity::Tokenize(std::string_view str, char sep,
 #if (defined(WIN32) || defined(_WIN32) || defined(__WIN32__))
 struct tm* localtime_r(time_t const* time, struct tm *result)
 {
-    localtime_s(result, time);
+    if (localtime_s(result, time) != 0)
+        return nullptr;
     return result;
 }
+struct tm* gmtime_r(time_t const* time, struct tm* result)
+{
+    if (gmtime_s(result, time) != 0)
+        return nullptr;
+    return result;
+}
+time_t timegm(struct tm* tm)
+{
+    return _mkgmtime(tm);
+}
 #endif
 
 tm TimeBreakdown(time_t time)
@@ -70,17 +81,6 @@ tm TimeBreakdown(time_t time)
     return timeLocal;
 }
 
-time_t LocalTimeToUTCTime(time_t time)
-{
-#if (defined(WIN32) || defined(_WIN32) || defined(__WIN32__))
-    return time + _timezone;
-#elif defined(__DragonFly__) || defined(__FreeBSD__) || defined(__NetBSD__) || defined(__OpenBSD__)
-    return timegm(gmtime(&time));
-#else
-    return time + timezone;
-#endif
-}
-
 time_t GetLocalHourTimestamp(time_t time, uint8 hour, bool onlyAfterTime)
 {
     tm timeLocal = TimeBreakdown(time);
diff --git a/src/common/Utilities/Util.h b/src/common/Utilities/Util.h
index be4a68d7788..334b3ab6ac0 100644
--- a/src/common/Utilities/Util.h
+++ b/src/common/Utilities/Util.h
@@ -54,8 +54,9 @@ TC_COMMON_API Optional<int64> MoneyStringToMoney(std::string const& moneyString)
 
 #if (defined(WIN32) || defined(_WIN32) || defined(__WIN32__))
 TC_COMMON_API struct tm* localtime_r(time_t const* time, struct tm *result);
+TC_COMMON_API struct tm* gmtime_r(time_t const* time, struct tm *result);
+TC_COMMON_API time_t timegm(struct tm* tm);
 #endif
-TC_COMMON_API time_t LocalTimeToUTCTime(time_t time);
 TC_COMMON_API time_t GetLocalHourTimestamp(time_t time, uint8 hour, bool onlyAfterTime = true);
 TC_COMMON_API tm TimeBreakdown(time_t t);
 
diff --git a/src/server/bnetserver/Server/Session.cpp b/src/server/bnetserver/Server/Session.cpp
index 6e5b16cd477..95c46418a7d 100644
--- a/src/server/bnetserver/Server/Session.cpp
+++ b/src/server/bnetserver/Server/Session.cpp
@@ -21,13 +21,17 @@
 #include "CryptoRandom.h"
 #include "DatabaseEnv.h"
 #include "Errors.h"
+#include "Hash.h"
 #include "IPLocation.h"
-#include "QueryCallback.h"
 #include "LoginRESTService.h"
+#include "MapUtils.h"
 #include "ProtobufJSON.h"
+#include "QueryCallback.h"
 #include "RealmList.h"
-#include "ServiceDispatcher.h"
 #include "RealmList.pb.h"
+#include "ServiceDispatcher.h"
+#include "Timezone.h"
+#include <rapidjson/document.h>
 #include <zlib.h>
 
 void Battlenet::Session::AccountInfo::LoadResult(PreparedQueryResult result)
@@ -229,6 +233,26 @@ uint32 Battlenet::Session::HandleLogon(authentication::v1::LogonRequest const* l
     _os = logonRequest->platform();
     _build = logonRequest->application_version();
 
+    _timezoneOffset = [&]
+    {
+        if (!logonRequest->has_device_id())
+            return 0min;
+
+        rapidjson::Document doc;
+        doc.Parse(logonRequest->device_id());
+        if (doc.HasParseError())
+            return 0min;
+
+        auto itr = doc.FindMember("UTCO");
+        if (itr == doc.MemberEnd())
+            return 0min;
+
+        if (!itr->value.IsUint())
+            return 0min;
+
+        return Trinity::Timezone::GetOffsetByHash(itr->value.GetUint());
+    }();
+
     if (logonRequest->has_cached_web_credentials())
         return VerifyWebCredentials(logonRequest->cached_web_credentials(), continuation);
 
@@ -670,7 +694,8 @@ uint32 Battlenet::Session::GetRealmList(std::unordered_map<std::string, Variant
 uint32 Battlenet::Session::JoinRealm(std::unordered_map<std::string, Variant const*> const& params, game_utilities::v1::ClientResponse* response)
 {
     if (Variant const* realmAddress = GetParam(params, "Param_RealmAddress"))
-        return sRealmList->JoinRealm(realmAddress->uint_value(), _build, GetRemoteIpAddress(), _clientSecret, GetLocaleByName(_locale), _os, _gameAccountInfo->Name, response);
+        return sRealmList->JoinRealm(realmAddress->uint_value(), _build, GetRemoteIpAddress(), _clientSecret, GetLocaleByName(_locale),
+            _os, _timezoneOffset, _gameAccountInfo->Name, response);
 
     return ERROR_WOW_SERVICES_INVALID_JOIN_TICKET;
 }
diff --git a/src/server/bnetserver/Server/Session.h b/src/server/bnetserver/Server/Session.h
index fd375b3a19a..01167d38a0b 100644
--- a/src/server/bnetserver/Server/Session.h
+++ b/src/server/bnetserver/Server/Session.h
@@ -19,6 +19,7 @@
 #define Session_h__
 
 #include "AsyncCallbackProcessor.h"
+#include "Duration.h"
 #include "Realm.h"
 #include "SslContext.h"
 #include "SslSocket.h"
@@ -173,6 +174,7 @@ namespace Battlenet
         std::string _locale;
         std::string _os;
         uint32 _build;
+        Minutes _timezoneOffset;
 
         std::string _ipCountry;
 
diff --git a/src/server/database/Database/Implementation/LoginDatabase.cpp b/src/server/database/Database/Implementation/LoginDatabase.cpp
index 0b9fd4e8f89..5745a063e53 100644
--- a/src/server/database/Database/Implementation/LoginDatabase.cpp
+++ b/src/server/database/Database/Implementation/LoginDatabase.cpp
@@ -39,7 +39,7 @@ void LoginDatabaseConnection::DoPrepareStatements()
     PrepareStatement(LOGIN_UPD_LOGON, "UPDATE account SET salt = ?, verifier = ? WHERE id = ?", CONNECTION_ASYNC);
     PrepareStatement(LOGIN_SEL_ACCOUNT_ID_BY_NAME, "SELECT id FROM account WHERE username = ?", CONNECTION_SYNCH);
     PrepareStatement(LOGIN_SEL_ACCOUNT_LIST_BY_NAME, "SELECT id, username FROM account WHERE username = ?", CONNECTION_SYNCH);
-    PrepareStatement(LOGIN_SEL_ACCOUNT_INFO_BY_NAME, "SELECT a.id, a.session_key_bnet, ba.last_ip, ba.locked, ba.lock_country, a.expansion, a.mutetime, ba.locale, a.recruiter, a.os, ba.id, aa.SecurityLevel, "
+    PrepareStatement(LOGIN_SEL_ACCOUNT_INFO_BY_NAME, "SELECT a.id, a.session_key_bnet, ba.last_ip, ba.locked, ba.lock_country, a.expansion, a.mutetime, ba.locale, a.recruiter, a.os, a.timezone_offset, ba.id, aa.SecurityLevel, "
         "bab.unbandate > UNIX_TIMESTAMP() OR bab.unbandate = bab.bandate, ab.unbandate > UNIX_TIMESTAMP() OR ab.unbandate = ab.bandate, r.id "
         "FROM account a LEFT JOIN account r ON a.id = r.recruiter LEFT JOIN battlenet_accounts ba ON a.battlenet_account = ba.id "
         "LEFT JOIN account_access aa ON a.id = aa.AccountID AND aa.RealmID IN (-1, ?) LEFT JOIN battlenet_account_bans bab ON ba.id = bab.id LEFT JOIN account_banned ab ON a.id = ab.id AND ab.active = 1 "
@@ -129,7 +129,7 @@ void LoginDatabaseConnection::DoPrepareStatements()
         " FROM battlenet_accounts ba LEFT JOIN battlenet_account_bans bab ON ba.id = bab.id LEFT JOIN account a ON ba.id = a.battlenet_account"
         " LEFT JOIN account_banned ab ON a.id = ab.id AND ab.active = 1 LEFT JOIN account_access aa ON a.id = aa.AccountID AND aa.RealmID = -1 WHERE ba.LoginTicket = ? ORDER BY a.id", CONNECTION_ASYNC);
     PrepareStatement(LOGIN_UPD_BNET_LAST_LOGIN_INFO, "UPDATE battlenet_accounts SET last_ip = ?, last_login = NOW(), locale = ?, failed_logins = 0, os = ? WHERE id = ?", CONNECTION_ASYNC);
-    PrepareStatement(LOGIN_UPD_BNET_GAME_ACCOUNT_LOGIN_INFO, "UPDATE account SET session_key_bnet = ?, last_ip = ?, last_login = NOW(), locale = ?, failed_logins = 0, os = ? WHERE username = ?", CONNECTION_SYNCH);
+    PrepareStatement(LOGIN_UPD_BNET_GAME_ACCOUNT_LOGIN_INFO, "UPDATE account SET session_key_bnet = ?, last_ip = ?, last_login = NOW(), locale = ?, failed_logins = 0, os = ?, timezone_offset = ? WHERE username = ?", CONNECTION_SYNCH);
     PrepareStatement(LOGIN_SEL_BNET_CHARACTER_COUNTS_BY_ACCOUNT_ID, "SELECT rc.acctid, rc.numchars, r.id, r.Region, r.Battlegroup FROM realmcharacters rc INNER JOIN realmlist r ON rc.realmid = r.id WHERE rc.acctid = ?", CONNECTION_ASYNC);
     PrepareStatement(LOGIN_SEL_BNET_CHARACTER_COUNTS_BY_BNET_ID, "SELECT rc.acctid, rc.numchars, r.id, r.Region, r.Battlegroup FROM realmcharacters rc INNER JOIN realmlist r ON rc.realmid = r.id LEFT JOIN account a ON rc.acctid = a.id WHERE a.battlenet_account = ?", CONNECTION_ASYNC);
     PrepareStatement(LOGIN_SEL_BNET_LAST_PLAYER_CHARACTERS, "SELECT lpc.accountId, lpc.region, lpc.battlegroup, lpc.realmId, lpc.characterName, lpc.characterGUID, lpc.lastPlayedTime FROM account_last_played_character lpc LEFT JOIN account a ON lpc.accountId = a.id WHERE a.battlenet_account = ?", CONNECTION_ASYNC);
diff --git a/src/server/game/Achievements/AchievementMgr.cpp b/src/server/game/Achievements/AchievementMgr.cpp
index 46891c35031..a2b401215f2 100644
--- a/src/server/game/Achievements/AchievementMgr.cpp
+++ b/src/server/game/Achievements/AchievementMgr.cpp
@@ -370,42 +370,42 @@ void PlayerAchievementMgr::SendAllData(Player const* /*receiver*/) const
         if (!achievement)
             continue;
 
-        WorldPackets::Achievement::EarnedAchievement earned;
+        WorldPackets::Achievement::EarnedAchievement& earned = achievementData.Data.Earned.emplace_back();
         earned.Id = completedAchievement.first;
-        earned.Date = completedAchievement.second.Date;
+        earned.Date.SetUtcTimeFromUnixTime(completedAchievement.second.Date);
+        earned.Date += _owner->GetSession()->GetTimezoneOffset();
         if (!(achievement->Flags & ACHIEVEMENT_FLAG_ACCOUNT))
         {
             earned.Owner = _owner->GetGUID();
             earned.VirtualRealmAddress = earned.NativeRealmAddress = GetVirtualRealmAddress();
         }
-        achievementData.Data.Earned.push_back(earned);
     }
 
     for (std::pair<uint32 const, CriteriaProgress> const& criteriaProgres : _criteriaProgress)
     {
         Criteria const* criteria = sCriteriaMgr->GetCriteria(criteriaProgres.first);
 
-        WorldPackets::Achievement::CriteriaProgress progress;
+        WorldPackets::Achievement::CriteriaProgress& progress = achievementData.Data.Progress.emplace_back();
         progress.Id = criteriaProgres.first;
         progress.Quantity = criteriaProgres.second.Counter;
         progress.Player = criteriaProgres.second.PlayerGUID;
         progress.Flags = 0;
-        progress.Date = criteriaProgres.second.Date;
+        progress.Date.SetUtcTimeFromUnixTime(criteriaProgres.second.Date);
+        progress.Date += _owner->GetSession()->GetTimezoneOffset();
         progress.TimeFromStart = Seconds::zero();
         progress.TimeFromCreate = Seconds::zero();
-        achievementData.Data.Progress.push_back(progress);
 
         if (criteria->FlagsCu & CRITERIA_FLAG_CU_ACCOUNT)
         {
-            WorldPackets::Achievement::CriteriaProgress progress;
-            progress.Id = criteriaProgres.first;
-            progress.Quantity = criteriaProgres.second.Counter;
-            progress.Player = _owner->GetSession()->GetBattlenetAccountGUID();
-            progress.Flags = 0;
-            progress.Date = criteriaProgres.second.Date;
-            progress.TimeFromStart = Seconds::zero();
-            progress.TimeFromCreate = Seconds::zero();
-            allAccountCriteria.Progress.push_back(progress);
+            WorldPackets::Achievement::CriteriaProgress& accountProgress = allAccountCriteria.Progress.emplace_back();
+            accountProgress.Id = criteriaProgres.first;
+            accountProgress.Quantity = criteriaProgres.second.Counter;
+            accountProgress.Player = _owner->GetSession()->GetBattlenetAccountGUID();
+            accountProgress.Flags = 0;
+            accountProgress.Date.SetUtcTimeFromUnixTime(criteriaProgres.second.Date);
+            accountProgress.Date += _owner->GetSession()->GetTimezoneOffset();
+            accountProgress.TimeFromStart = Seconds::zero();
+            accountProgress.TimeFromCreate = Seconds::zero();
         }
     }
 
@@ -429,28 +429,28 @@ void PlayerAchievementMgr::SendAchievementInfo(Player* receiver, uint32 /*achiev
         if (!achievement)
             continue;
 
-        WorldPackets::Achievement::EarnedAchievement earned;
+        WorldPackets::Achievement::EarnedAchievement& earned = inspectedAchievements.Data.Earned.emplace_back();
         earned.Id = completedAchievement.first;
-        earned.Date = completedAchievement.second.Date;
+        earned.Date.SetUtcTimeFromUnixTime(completedAchievement.second.Date);
+        earned.Date += receiver->GetSession()->GetTimezoneOffset();
         if (!(achievement->Flags & ACHIEVEMENT_FLAG_ACCOUNT))
         {
             earned.Owner = _owner->GetGUID();
             earned.VirtualRealmAddress = earned.NativeRealmAddress = GetVirtualRealmAddress();
         }
-        inspectedAchievements.Data.Earned.push_back(earned);
     }
 
     for (std::pair<uint32 const, CriteriaProgress> const& criteriaProgres : _criteriaProgress)
     {
-        WorldPackets::Achievement::CriteriaProgress progress;
+        WorldPackets::Achievement::CriteriaProgress& progress = inspectedAchievements.Data.Progress.emplace_back();
         progress.Id = criteriaProgres.first;
         progress.Quantity = criteriaProgres.second.Counter;
         progress.Player = criteriaProgres.second.PlayerGUID;
         progress.Flags = 0;
-        progress.Date = criteriaProgres.second.Date;
+        progress.Date.SetUtcTimeFromUnixTime(criteriaProgres.second.Date);
+        progress.Date += receiver->GetSession()->GetTimezoneOffset();
         progress.TimeFromStart = Seconds::zero();
         progress.TimeFromCreate = Seconds::zero();
-        inspectedAchievements.Data.Progress.push_back(progress);
     }
 
     receiver->SendDirectMessage(inspectedAchievements.Write());
@@ -571,7 +571,8 @@ void PlayerAchievementMgr::SendCriteriaUpdate(Criteria const* criteria, Criteria
         if (criteria->Entry->StartTimer)
             criteriaUpdate.Progress.Flags = timedCompleted ? 1 : 0; // 1 is for keeping the counter at 0 in client
 
-        criteriaUpdate.Progress.Date = progress->Date;
+        criteriaUpdate.Progress.Date.SetUtcTimeFromUnixTime(progress->Date);
+        criteriaUpdate.Progress.Date += _owner->GetSession()->GetTimezoneOffset();
         criteriaUpdate.Progress.TimeFromStart = timeElapsed;
         criteriaUpdate.Progress.TimeFromCreate = Seconds::zero();
 
@@ -588,7 +589,8 @@ void PlayerAchievementMgr::SendCriteriaUpdate(Criteria const* criteria, Criteria
         if (criteria->Entry->StartTimer)
             criteriaUpdate.Flags = timedCompleted ? 1 : 0; // 1 is for keeping the counter at 0 in client
 
-        criteriaUpdate.CurrentTime = progress->Date;
+        criteriaUpdate.CurrentTime.SetUtcTimeFromUnixTime(progress->Date);
+        criteriaUpdate.CurrentTime += _owner->GetSession()->GetTimezoneOffset();
         criteriaUpdate.ElapsedTime = timeElapsed;
         criteriaUpdate.CreationTime = 0;
 
@@ -639,16 +641,26 @@ void PlayerAchievementMgr::SendAchievementEarned(AchievementEntry const* achieve
         }
     }
 
-    WorldPackets::Achievement::AchievementEarned achievementEarned;
-    achievementEarned.Sender = _owner->GetGUID();
-    achievementEarned.Earner = _owner->GetGUID();
-    achievementEarned.EarnerNativeRealm = achievementEarned.EarnerVirtualRealm = GetVirtualRealmAddress();
-    achievementEarned.AchievementID = achievement->ID;
-    achievementEarned.Time = GameTime::GetGameTime();
+    auto achievementEarnedBuilder = [&](Player const* receiver)
+    {
+        WorldPackets::Achievement::AchievementEarned achievementEarned;
+        achievementEarned.Sender = _owner->GetGUID();
+        achievementEarned.Earner = _owner->GetGUID();
+        achievementEarned.EarnerNativeRealm = achievementEarned.EarnerVirtualRealm = GetVirtualRealmAddress();
+        achievementEarned.AchievementID = achievement->ID;
+        achievementEarned.Time = *GameTime::GetUtcWowTime();
+        achievementEarned.Time += receiver->GetSession()->GetTimezoneOffset();
+        receiver->SendDirectMessage(achievementEarned.Write());
+    };
+
     if (!(achievement->Flags & ACHIEVEMENT_FLAG_TRACKING_FLAG))
-        _owner->SendMessageToSetInRange(achievementEarned.Write(), sWorld->getFloatConfig(CONFIG_LISTEN_RANGE_SAY), true);
+    {
+        float dist = sWorld->getFloatConfig(CONFIG_LISTEN_RANGE_SAY);
+        Trinity::MessageDistDeliverer notifier(_owner, achievementEarnedBuilder, dist);
+        Cell::VisitWorldObjects(_owner, notifier, dist);
+    }
     else
-        _owner->SendDirectMessage(achievementEarned.Write());
+        achievementEarnedBuilder(_owner);
 }
 
 void PlayerAchievementMgr::SendPacket(WorldPacket const* data) const
@@ -672,11 +684,16 @@ void GuildAchievementMgr::Reset()
     ObjectGuid guid = _owner->GetGUID();
     for (std::pair<uint32 const, CompletedAchievementData> const& completedAchievement : _completedAchievements)
     {
-        WorldPackets::Achievement::GuildAchievementDeleted guildAchievementDeleted;
-        guildAchievementDeleted.AchievementID = completedAchievement.first;
-        guildAchievementDeleted.GuildGUID = guid;
-        guildAchievementDeleted.TimeDeleted = GameTime::GetGameTime();
-        SendPacket(guildAchievementDeleted.Write());
+        auto packetBuilder = [&](Player const* receiver)
+        {
+            WorldPackets::Achievement::GuildAchievementDeleted guildAchievementDeleted;
+            guildAchievementDeleted.AchievementID = completedAchievement.first;
+            guildAchievementDeleted.GuildGUID = guid;
+            guildAchievementDeleted.TimeDeleted = *GameTime::GetUtcWowTime();
+            guildAchievementDeleted.TimeDeleted += receiver->GetSession()->GetTimezoneOffset();
+            receiver->SendDirectMessage(guildAchievementDeleted.Write());
+        };
+        _owner->BroadcastWorker(packetBuilder);
     }
 
     _achievementPoints = 0;
@@ -823,10 +840,10 @@ void GuildAchievementMgr::SendAllData(Player const* receiver) const
         if (!achievement)
             continue;
 
-        WorldPackets::Achievement::EarnedAchievement earned;
+        WorldPackets::Achievement::EarnedAchievement& earned = allGuildAchievements.Earned.emplace_back();
         earned.Id = completedAchievement.first;
-        earned.Date = completedAchievement.second.Date;
-        allGuildAchievements.Earned.push_back(earned);
+        earned.Date.SetUtcTimeFromUnixTime(completedAchievement.second.Date);
+        earned.Date += receiver->GetSession()->GetTimezoneOffset();
     }
 
     receiver->SendDirectMessage(allGuildAchievements.Write());
@@ -839,23 +856,22 @@ void GuildAchievementMgr::SendAchievementInfo(Player* receiver, uint32 achieveme
     {
         if (CriteriaTree const* tree = sCriteriaMgr->GetCriteriaTree(achievement->CriteriaTree))
         {
-            CriteriaMgr::WalkCriteriaTree(tree, [this, &guildCriteriaUpdate](CriteriaTree const* node)
+            CriteriaMgr::WalkCriteriaTree(tree, [this, &guildCriteriaUpdate, receiver](CriteriaTree const* node)
             {
                 if (node->Criteria)
                 {
                     auto progress = this->_criteriaProgress.find(node->Criteria->ID);
                     if (progress != this->_criteriaProgress.end())
                     {
-                        WorldPackets::Achievement::GuildCriteriaProgress guildCriteriaProgress;
+                        WorldPackets::Achievement::GuildCriteriaProgress& guildCriteriaProgress = guildCriteriaUpdate.Progress.emplace_back();
                         guildCriteriaProgress.CriteriaID = node->Criteria->ID;
                         guildCriteriaProgress.DateCreated = 0;
                         guildCriteriaProgress.DateStarted = 0;
-                        guildCriteriaProgress.DateUpdated = progress->second.Date;
+                        guildCriteriaProgress.DateUpdated.SetUtcTimeFromUnixTime(progress->second.Date);
+                        guildCriteriaProgress.DateUpdated += receiver->GetSession()->GetTimezoneOffset();
                         guildCriteriaProgress.Quantity = progress->second.Counter;
                         guildCriteriaProgress.PlayerGUID = progress->second.PlayerGUID;
                         guildCriteriaProgress.Flags = 0;
-
-                        guildCriteriaUpdate.Progress.push_back(guildCriteriaProgress);
                     }
                 }
             });
@@ -876,16 +892,15 @@ void GuildAchievementMgr::SendAllTrackedCriterias(Player* receiver, std::set<uin
         if (progress == _criteriaProgress.end())
             continue;
 
-        WorldPackets::Achievement::GuildCriteriaProgress guildCriteriaProgress;
+        WorldPackets::Achievement::GuildCriteriaProgress& guildCriteriaProgress = guildCriteriaUpdate.Progress.emplace_back();
         guildCriteriaProgress.CriteriaID = criteriaId;
         guildCriteriaProgress.DateCreated = 0;
         guildCriteriaProgress.DateStarted = 0;
-        guildCriteriaProgress.DateUpdated = progress->second.Date;
+        guildCriteriaProgress.DateUpdated.SetUtcTimeFromUnixTime(progress->second.Date);
+        guildCriteriaProgress.DateUpdated += receiver->GetSession()->GetTimezoneOffset();
         guildCriteriaProgress.Quantity = progress->second.Counter;
         guildCriteriaProgress.PlayerGUID = progress->second.PlayerGUID;
         guildCriteriaProgress.Flags = 0;
-
-        guildCriteriaUpdate.Progress.push_back(guildCriteriaProgress);
     }
 
     receiver->SendDirectMessage(guildCriteriaUpdate.Write());
@@ -949,19 +964,21 @@ void GuildAchievementMgr::CompletedAchievement(AchievementEntry const* achieveme
 
 void GuildAchievementMgr::SendCriteriaUpdate(Criteria const* entry, CriteriaProgress const* progress, Seconds /*timeElapsed*/, bool /*timedCompleted*/) const
 {
-    WorldPackets::Achievement::GuildCriteriaUpdate guildCriteriaUpdate;
-    guildCriteriaUpdate.Progress.resize(1);
-
-    WorldPackets::Achievement::GuildCriteriaProgress& guildCriteriaProgress = guildCriteriaUpdate.Progress[0];
-    guildCriteriaProgress.CriteriaID = entry->ID;
-    guildCriteriaProgress.DateCreated = 0;
-    guildCriteriaProgress.DateStarted = 0;
-    guildCriteriaProgress.DateUpdated = progress->Date;
-    guildCriteriaProgress.Quantity = progress->Counter;
-    guildCriteriaProgress.PlayerGUID = progress->PlayerGUID;
-    guildCriteriaProgress.Flags = 0;
-
-    _owner->BroadcastPacketIfTrackingAchievement(guildCriteriaUpdate.Write(), entry->ID);
+    for (Player const* member : _owner->GetMembersTrackingCriteria(entry->ID))
+    {
+        WorldPackets::Achievement::GuildCriteriaUpdate guildCriteriaUpdate;
+        WorldPackets::Achievement::GuildCriteriaProgress& guildCriteriaProgress = guildCriteriaUpdate.Progress.emplace_back();
+        guildCriteriaProgress.CriteriaID = entry->ID;
+        guildCriteriaProgress.DateCreated = 0;
+        guildCriteriaProgress.DateStarted = 0;
+        guildCriteriaProgress.DateUpdated.SetUtcTimeFromUnixTime(progress->Date);
+        guildCriteriaProgress.DateUpdated += member->GetSession()->GetTimezoneOffset();
+        guildCriteriaProgress.Quantity = progress->Counter;
+        guildCriteriaProgress.PlayerGUID = progress->PlayerGUID;
+        guildCriteriaProgress.Flags = 0;
+
+        member->SendDirectMessage(guildCriteriaUpdate.Write());
+    }
 }
 
 void GuildAchievementMgr::SendCriteriaProgressRemoved(uint32 criteriaId)
@@ -985,11 +1002,16 @@ void GuildAchievementMgr::SendAchievementEarned(AchievementEntry const* achievem
         sWorld->SendGlobalMessage(serverFirstAchievement.Write());
     }
 
-    WorldPackets::Achievement::GuildAchievementEarned guildAchievementEarned;
-    guildAchievementEarned.AchievementID = achievement->ID;
-    guildAchievementEarned.GuildGUID = _owner->GetGUID();
-    guildAchievementEarned.TimeEarned = GameTime::GetGameTime();
-    SendPacket(guildAchievementEarned.Write());
+    auto guildAchievementEarnedBuilder = [&](Player const* receiver)
+    {
+        WorldPackets::Achievement::GuildAchievementEarned guildAchievementEarned;
+        guildAchievementEarned.AchievementID = achievement->ID;
+        guildAchievementEarned.GuildGUID = _owner->GetGUID();
+        guildAchievementEarned.TimeEarned = *GameTime::GetUtcWowTime();
+        guildAchievementEarned.TimeEarned += receiver->GetSession()->GetTimezoneOffset();
+        receiver->SendDirectMessage(guildAchievementEarned.Write());
+    };
+    _owner->BroadcastWorker(guildAchievementEarnedBuilder);
 }
 
 void GuildAchievementMgr::SendPacket(WorldPacket const* data) const
diff --git a/src/server/game/Achievements/CriteriaHandler.cpp b/src/server/game/Achievements/CriteriaHandler.cpp
index a821b11c642..8d9a54c8789 100644
--- a/src/server/game/Achievements/CriteriaHandler.cpp
+++ b/src/server/game/Achievements/CriteriaHandler.cpp
@@ -49,6 +49,7 @@
 #include "World.h"
 #include "WorldSession.h"
 #include "WorldStateMgr.h"
+#include "WowTime.h"
 
 bool CriteriaData::IsValid(Criteria const* criteria)
 {
@@ -2230,14 +2231,12 @@ bool CriteriaHandler::ModifierSatisfied(ModifierTreeEntry const* modifier, uint6
             break;
         case ModifierTreeType::TimeBetween: // 109
         {
-            ByteBuffer unpacker;
-            unpacker << reqValue;
-            time_t from = unpacker.ReadPackedTime();
-            unpacker.rpos(0);
-            unpacker.wpos(0);
-            unpacker << secondaryAsset;
-            time_t to = unpacker.ReadPackedTime();
-            if (GameTime::GetGameTime() < from || GameTime::GetGameTime() > to)
+            WowTime from;
+            from.SetPackedTime(reqValue);
+            WowTime to;
+            to.SetPackedTime(secondaryAsset);
+
+            if (!GameTime::GetWowTime()->IsInRange(from, to))
                 return false;
             break;
         }
diff --git a/src/server/game/AuctionHouse/AuctionHouseMgr.cpp b/src/server/game/AuctionHouse/AuctionHouseMgr.cpp
index 0d149078279..21332e20171 100644
--- a/src/server/game/AuctionHouse/AuctionHouseMgr.cpp
+++ b/src/server/game/AuctionHouse/AuctionHouseMgr.cpp
@@ -34,11 +34,11 @@
 #include "ObjectAccessor.h"
 #include "ObjectMgr.h"
 #include "Player.h"
-#include "Realm.h"
 #include "ScriptMgr.h"
+#include "Timezone.h"
 #include "World.h"
-#include "WorldPacket.h"
 #include "WorldSession.h"
+#include "WowTime.h"
 #include <boost/dynamic_bitset.hpp>
 #include <numeric>
 #include <sstream>
@@ -1911,13 +1911,13 @@ void AuctionHouseObject::SendAuctionInvoice(AuctionPosting const* auction, Playe
     // owner exist (online or offline)
     if ((owner || sCharacterCache->HasCharacterCacheEntry(auction->Owner)) && !sAuctionBotConfig->IsBotChar(auction->Owner))
     {
-        ByteBuffer tempBuffer;
-        tempBuffer.AppendPackedTime(GameTime::GetGameTime() + sWorld->getIntConfig(CONFIG_MAIL_DELIVERY_DELAY));
-        uint32 eta = tempBuffer.read<uint32>();
+        WowTime eta = *GameTime::GetUtcWowTime();
+        eta += Seconds(sWorld->getIntConfig(CONFIG_MAIL_DELIVERY_DELAY));
+        eta += owner->GetSession()->GetTimezoneOffset();
 
         MailDraft(AuctionHouseMgr::BuildItemAuctionMailSubject(AuctionMailType::Invoice, auction),
             AuctionHouseMgr::BuildAuctionInvoiceMailBody(auction->Bidder, auction->BidAmount, auction->BuyoutOrUnitPrice, auction->Deposit,
-                CalculateAuctionHouseCut(auction->BidAmount), sWorld->getIntConfig(CONFIG_MAIL_DELIVERY_DELAY), eta))
+                CalculateAuctionHouseCut(auction->BidAmount), sWorld->getIntConfig(CONFIG_MAIL_DELIVERY_DELAY), eta.GetPackedTime()))
             .SendMailTo(trans, MailReceiver(owner, auction->Owner), this, MAIL_CHECK_MASK_COPIED);
     }
 }
diff --git a/src/server/game/Calendar/CalendarMgr.cpp b/src/server/game/Calendar/CalendarMgr.cpp
index fdceaa3762e..66f8ab9cb27 100644
--- a/src/server/game/Calendar/CalendarMgr.cpp
+++ b/src/server/game/Calendar/CalendarMgr.cpp
@@ -24,12 +24,16 @@
 #include "GuildMgr.h"
 #include "Log.h"
 #include "Mail.h"
+#include "MapUtils.h"
 #include "ObjectAccessor.h"
 #include "Player.h"
+#include "StringConvert.h"
+#include "WorldSession.h"
+#include "WowTime.h"
 #include <sstream>
 
 CalendarInvite::CalendarInvite() : _inviteId(1), _eventId(0), _invitee(), _senderGUID(), _responseTime(0),
-_status(CALENDAR_STATUS_INVITED), _rank(CALENDAR_RANK_PLAYER), _note("") { }
+_status(CALENDAR_STATUS_INVITED), _rank(CALENDAR_RANK_PLAYER), _note() { }
 
 CalendarInvite::~CalendarInvite()
 {
@@ -184,7 +188,6 @@ void CalendarMgr::RemoveEvent(CalendarEvent* calendarEvent, ObjectGuid remover)
 
     CharacterDatabaseTransaction trans = CharacterDatabase.BeginTransaction();
     CharacterDatabasePreparedStatement* stmt;
-    MailDraft mail(calendarEvent->BuildCalendarMailSubject(remover), calendarEvent->BuildCalendarMailBody());
 
     CalendarInviteStore& eventInvites = _invites[calendarEvent->GetEventId()];
     for (size_t i = 0; i < eventInvites.size(); ++i)
@@ -197,7 +200,10 @@ void CalendarMgr::RemoveEvent(CalendarEvent* calendarEvent, ObjectGuid remover)
         // guild events only? check invite status here?
         // When an event is deleted, all invited (accepted/declined? - verify) guildies are notified via in-game mail. (wowwiki)
         if (!remover.IsEmpty() && invite->GetInviteeGUID() != remover)
+        {
+            MailDraft mail(calendarEvent->BuildCalendarMailSubject(remover), calendarEvent->BuildCalendarMailBody(ObjectAccessor::FindConnectedPlayer(invite->GetInviteeGUID())));
             mail.SendMailTo(trans, MailReceiver(invite->GetInviteeGUID().GetCounter()), calendarEvent, MAIL_CHECK_MASK_COPIED);
+        }
 
         delete invite;
     }
@@ -375,7 +381,7 @@ void CalendarMgr::DeleteOldEvents()
     }
 }
 
-CalendarEventStore CalendarMgr::GetEventsCreatedBy(ObjectGuid guid, bool includeGuildEvents)
+CalendarEventStore CalendarMgr::GetEventsCreatedBy(ObjectGuid guid, bool includeGuildEvents) const
 {
     CalendarEventStore result;
     for (CalendarEventStore::const_iterator itr = _events.begin(); itr != _events.end(); ++itr)
@@ -385,7 +391,7 @@ CalendarEventStore CalendarMgr::GetEventsCreatedBy(ObjectGuid guid, bool include
     return result;
 }
 
-CalendarEventStore CalendarMgr::GetGuildEvents(ObjectGuid::LowType guildId)
+CalendarEventStore CalendarMgr::GetGuildEvents(ObjectGuid::LowType guildId) const
 {
     CalendarEventStore result;
 
@@ -400,7 +406,7 @@ CalendarEventStore CalendarMgr::GetGuildEvents(ObjectGuid::LowType guildId)
     return result;
 }
 
-CalendarEventStore CalendarMgr::GetPlayerEvents(ObjectGuid guid)
+CalendarEventStore CalendarMgr::GetPlayerEvents(ObjectGuid guid) const
 {
     CalendarEventStore events;
 
@@ -419,12 +425,16 @@ CalendarEventStore CalendarMgr::GetPlayerEvents(ObjectGuid guid)
     return events;
 }
 
-CalendarInviteStore const& CalendarMgr::GetEventInvites(uint64 eventId)
+CalendarInviteStore CalendarMgr::GetEventInvites(uint64 eventId) const
 {
-    return _invites[eventId];
+    CalendarInviteStore invites;
+    if (CalendarInviteStore const* invitesStore = Trinity::Containers::MapGetValuePtr(_invites, eventId))
+        invites = *invitesStore;
+
+    return invites;
 }
 
-CalendarInviteStore CalendarMgr::GetPlayerInvites(ObjectGuid guid)
+CalendarInviteStore CalendarMgr::GetPlayerInvites(ObjectGuid guid) const
 {
     CalendarInviteStore invites;
 
@@ -465,20 +475,17 @@ std::string CalendarEvent::BuildCalendarMailSubject(ObjectGuid remover) const
     return strm.str();
 }
 
-std::string CalendarEvent::BuildCalendarMailBody() const
+std::string CalendarEvent::BuildCalendarMailBody(Player const* invitee) const
 {
-    WorldPacket data;
-    uint32 time;
-    std::ostringstream strm;
+    WowTime time;
+    time.SetUtcTimeFromUnixTime(_date);
+    if (invitee)
+        time += invitee->GetSession()->GetTimezoneOffset();
 
-    // we are supposed to send PackedTime so i used WorldPacket to pack it
-    data.AppendPackedTime(_date);
-    data >> time;
-    strm << time;
-    return strm.str();
+    return Trinity::ToString(time.GetPackedTime());
 }
 
-void CalendarMgr::SendCalendarEventInvite(CalendarInvite const& invite)
+void CalendarMgr::SendCalendarEventInvite(CalendarInvite const& invite) const
 {
     CalendarEvent* calendarEvent = GetEvent(invite.GetEventId());
 
@@ -487,71 +494,103 @@ void CalendarMgr::SendCalendarEventInvite(CalendarInvite const& invite)
 
     uint8 level = player ? player->GetLevel() : sCharacterCache->GetCharacterLevelByGuid(invitee);
 
-    WorldPackets::Calendar::CalendarInviteAdded packet;
-    packet.EventID = calendarEvent ? calendarEvent->GetEventId() : 0;
-    packet.InviteGuid = invitee;
-    packet.InviteID = calendarEvent ? invite.GetInviteId() : 0;
-    packet.Level = level;
-    packet.ResponseTime = invite.GetResponseTime();
-    packet.Status = invite.GetStatus();
-    packet.Type = calendarEvent ? calendarEvent->IsGuildEvent() : 0; // Correct ?
-    packet.ClearPending = calendarEvent ? !calendarEvent->IsGuildEvent() : true; // Correct ?
+    auto packetBuilder = [&](Player const* receiver)
+    {
+        WorldPackets::Calendar::CalendarInviteAdded packet;
+        packet.EventID = calendarEvent ? calendarEvent->GetEventId() : 0;
+        packet.InviteGuid = invitee;
+        packet.InviteID = calendarEvent ? invite.GetInviteId() : 0;
+        packet.Level = level;
+        packet.ResponseTime.SetUtcTimeFromUnixTime(invite.GetResponseTime());
+        packet.ResponseTime += receiver->GetSession()->GetTimezoneOffset();
+        packet.Status = invite.GetStatus();
+        packet.Type = calendarEvent ? calendarEvent->IsGuildEvent() : 0; // Correct ?
+        packet.ClearPending = calendarEvent ? !calendarEvent->IsGuildEvent() : true; // Correct ?
+
+        receiver->SendDirectMessage(packet.Write());
+    };
 
     if (!calendarEvent) // Pre-invite
     {
         if (Player* playerSender = ObjectAccessor::FindConnectedPlayer(invite.GetSenderGUID()))
-            playerSender->SendDirectMessage(packet.Write());
+            packetBuilder(playerSender);
     }
     else
     {
         if (calendarEvent->GetOwnerGUID() != invite.GetInviteeGUID()) // correct?
-            SendPacketToAllEventRelatives(packet.Write(), *calendarEvent);
+            for (Player* receiver : GetAllEventRelatives(*calendarEvent))
+                packetBuilder(receiver);
     }
 }
 
-void CalendarMgr::SendCalendarEventUpdateAlert(CalendarEvent const& calendarEvent, time_t originalDate)
+void CalendarMgr::SendCalendarEventUpdateAlert(CalendarEvent const& calendarEvent, time_t originalDate) const
 {
-    WorldPackets::Calendar::CalendarEventUpdatedAlert packet;
-    packet.ClearPending = true; // FIXME
-    packet.Date = calendarEvent.GetDate();
-    packet.Description = calendarEvent.GetDescription();
-    packet.EventClubID = calendarEvent.GetGuildId();
-    packet.EventID = calendarEvent.GetEventId();
-    packet.EventName = calendarEvent.GetTitle();
-    packet.EventType = calendarEvent.GetType();
-    packet.Flags = calendarEvent.GetFlags();
-    packet.LockDate = calendarEvent.GetLockDate(); // Always 0 ?
-    packet.OriginalDate = originalDate;
-    packet.TextureID = calendarEvent.GetTextureId();
+    auto packetBuilder = [&](Player const* receiver)
+    {
+        WorldPackets::Calendar::CalendarEventUpdatedAlert packet;
+        packet.ClearPending = true; // FIXME
+        packet.Date.SetUtcTimeFromUnixTime(calendarEvent.GetDate());
+        packet.Date += receiver->GetSession()->GetTimezoneOffset();
+        packet.Description = calendarEvent.GetDescription();
+        packet.EventClubID = calendarEvent.GetGuildId();
+        packet.EventID = calendarEvent.GetEventId();
+        packet.EventName = calendarEvent.GetTitle();
+        packet.EventType = calendarEvent.GetType();
+        packet.Flags = calendarEvent.GetFlags();
+        packet.LockDate.SetUtcTimeFromUnixTime(calendarEvent.GetLockDate()); // Always 0 ?
+        if (calendarEvent.GetLockDate())
+            packet.LockDate += receiver->GetSession()->GetTimezoneOffset();
+        packet.OriginalDate.SetUtcTimeFromUnixTime(originalDate);
+        packet.OriginalDate += receiver->GetSession()->GetTimezoneOffset();
+        packet.TextureID = calendarEvent.GetTextureId();
 
-    SendPacketToAllEventRelatives(packet.Write(), calendarEvent);
+        receiver->SendDirectMessage(packet.Write());
+    };
+
+    for (Player* receiver : GetAllEventRelatives(calendarEvent))
+        packetBuilder(receiver);
 }
 
-void CalendarMgr::SendCalendarEventStatus(CalendarEvent const& calendarEvent, CalendarInvite const& invite)
+void CalendarMgr::SendCalendarEventStatus(CalendarEvent const& calendarEvent, CalendarInvite const& invite) const
 {
-    WorldPackets::Calendar::CalendarInviteStatus packet;
-    packet.ClearPending = true; // FIXME
-    packet.Date = calendarEvent.GetDate();
-    packet.EventID = calendarEvent.GetEventId();
-    packet.Flags = calendarEvent.GetFlags();
-    packet.InviteGuid = invite.GetInviteeGUID();
-    packet.ResponseTime = invite.GetResponseTime();
-    packet.Status = invite.GetStatus();
+    auto packetBuilder = [&](Player const* receiver)
+    {
+        WorldPackets::Calendar::CalendarInviteStatus packet;
+        packet.ClearPending = true; // FIXME
+        packet.Date.SetUtcTimeFromUnixTime(calendarEvent.GetDate());
+        packet.Date += receiver->GetSession()->GetTimezoneOffset();
+        packet.EventID = calendarEvent.GetEventId();
+        packet.Flags = calendarEvent.GetFlags();
+        packet.InviteGuid = invite.GetInviteeGUID();
+        packet.ResponseTime.SetUtcTimeFromUnixTime(invite.GetResponseTime());
+        packet.ResponseTime += receiver->GetSession()->GetTimezoneOffset();
+        packet.Status = invite.GetStatus();
 
-    SendPacketToAllEventRelatives(packet.Write(), calendarEvent);
+        receiver->SendDirectMessage(packet.Write());
+    };
+
+    for (Player* receiver : GetAllEventRelatives(calendarEvent))
+        packetBuilder(receiver);
 }
 
-void CalendarMgr::SendCalendarEventRemovedAlert(CalendarEvent const& calendarEvent)
+void CalendarMgr::SendCalendarEventRemovedAlert(CalendarEvent const& calendarEvent) const
 {
-    WorldPackets::Calendar::CalendarEventRemovedAlert packet;
-    packet.ClearPending = true; // FIXME
-    packet.Date = calendarEvent.GetDate();
-    packet.EventID = calendarEvent.GetEventId();
+    auto packetBuilder = [&](Player const* receiver)
+    {
+        WorldPackets::Calendar::CalendarEventRemovedAlert packet;
+        packet.ClearPending = true; // FIXME
+        packet.Date.SetUtcTimeFromUnixTime(calendarEvent.GetDate());
+        packet.Date += receiver->GetSession()->GetTimezoneOffset();
+        packet.EventID = calendarEvent.GetEventId();
 
-    SendPacketToAllEventRelatives(packet.Write(), calendarEvent);
+        receiver->SendDirectMessage(packet.Write());
+    };
+
+    for (Player* receiver : GetAllEventRelatives(calendarEvent))
+        packetBuilder(receiver);
 }
 
-void CalendarMgr::SendCalendarEventInviteRemove(CalendarEvent const& calendarEvent, CalendarInvite const& invite, uint32 flags)
+void CalendarMgr::SendCalendarEventInviteRemove(CalendarEvent const& calendarEvent, CalendarInvite const& invite, uint32 flags) const
 {
     WorldPackets::Calendar::CalendarInviteRemoved packet;
     packet.ClearPending = true; // FIXME
@@ -562,7 +601,7 @@ void CalendarMgr::SendCalendarEventInviteRemove(CalendarEvent const& calendarEve
     SendPacketToAllEventRelatives(packet.Write(), calendarEvent);
 }
 
-void CalendarMgr::SendCalendarEventModeratorStatusAlert(CalendarEvent const& calendarEvent, CalendarInvite const& invite)
+void CalendarMgr::SendCalendarEventModeratorStatusAlert(CalendarEvent const& calendarEvent, CalendarInvite const& invite) const
 {
     WorldPackets::Calendar::CalendarModeratorStatus packet;
     packet.ClearPending = true; // FIXME
@@ -573,82 +612,94 @@ void CalendarMgr::SendCalendarEventModeratorStatusAlert(CalendarEvent const& cal
     SendPacketToAllEventRelatives(packet.Write(), calendarEvent);
 }
 
-void CalendarMgr::SendCalendarEventInviteAlert(CalendarEvent const& calendarEvent, CalendarInvite const& invite)
+void CalendarMgr::SendCalendarEventInviteAlert(CalendarEvent const& calendarEvent, CalendarInvite const& invite) const
 {
-    WorldPackets::Calendar::CalendarInviteAlert packet;
-    packet.Date = calendarEvent.GetDate();
-    packet.EventID = calendarEvent.GetEventId();
-    packet.EventName = calendarEvent.GetTitle();
-    packet.EventType = calendarEvent.GetType();
-    packet.Flags = calendarEvent.GetFlags();
-    packet.InviteID = invite.GetInviteId();
-    packet.InvitedByGuid = invite.GetSenderGUID();
-    packet.ModeratorStatus = invite.GetRank();
-    packet.OwnerGuid = calendarEvent.GetOwnerGUID();
-    packet.Status = invite.GetStatus();
-    packet.TextureID = calendarEvent.GetTextureId();
-    packet.EventClubID = calendarEvent.GetGuildId();
+    auto packetBuilder = [&](Player const* receiver)
+    {
+        WorldPackets::Calendar::CalendarInviteAlert packet;
+        packet.Date.SetUtcTimeFromUnixTime(calendarEvent.GetDate());
+        packet.Date += receiver->GetSession()->GetTimezoneOffset();
+        packet.EventID = calendarEvent.GetEventId();
+        packet.EventName = calendarEvent.GetTitle();
+        packet.EventType = calendarEvent.GetType();
+        packet.Flags = calendarEvent.GetFlags();
+        packet.InviteID = invite.GetInviteId();
+        packet.InvitedByGuid = invite.GetSenderGUID();
+        packet.ModeratorStatus = invite.GetRank();
+        packet.OwnerGuid = calendarEvent.GetOwnerGUID();
+        packet.Status = invite.GetStatus();
+        packet.TextureID = calendarEvent.GetTextureId();
+        packet.EventClubID = calendarEvent.GetGuildId();
+
+        receiver->SendDirectMessage(packet.Write());
+    };
 
     if (calendarEvent.IsGuildEvent() || calendarEvent.IsGuildAnnouncement())
     {
         if (Guild* guild = sGuildMgr->GetGuildById(calendarEvent.GetGuildId()))
-            guild->BroadcastPacket(packet.Write());
+            guild->BroadcastWorker(packetBuilder);
     }
     else if (Player* player = ObjectAccessor::FindConnectedPlayer(invite.GetInviteeGUID()))
-        player->SendDirectMessage(packet.Write());
+        packetBuilder(player);
 }
 
-void CalendarMgr::SendCalendarEvent(ObjectGuid guid, CalendarEvent const& calendarEvent, CalendarSendEventType sendType)
+void CalendarMgr::SendCalendarEvent(ObjectGuid guid, CalendarEvent const& calendarEvent, CalendarSendEventType sendType) const
 {
     Player* player = ObjectAccessor::FindConnectedPlayer(guid);
     if (!player)
         return;
 
-    CalendarInviteStore const& eventInviteeList = _invites[calendarEvent.GetEventId()];
-
     WorldPackets::Calendar::CalendarSendEvent packet;
-    packet.Date = calendarEvent.GetDate();
+    packet.Date.SetUtcTimeFromUnixTime(calendarEvent.GetDate());
+    packet.Date += player->GetSession()->GetTimezoneOffset();
     packet.Description = calendarEvent.GetDescription();
     packet.EventID = calendarEvent.GetEventId();
     packet.EventName = calendarEvent.GetTitle();
     packet.EventType = sendType;
     packet.Flags = calendarEvent.GetFlags();
     packet.GetEventType = calendarEvent.GetType();
-    packet.LockDate = calendarEvent.GetLockDate(); // Always 0 ?
+    packet.LockDate.SetUtcTimeFromUnixTime(calendarEvent.GetLockDate()); // Always 0 ?
+    if (calendarEvent.GetLockDate())
+        packet.LockDate += player->GetSession()->GetTimezoneOffset();
     packet.OwnerGuid = calendarEvent.GetOwnerGUID();
     packet.TextureID = calendarEvent.GetTextureId();
     packet.EventClubID = calendarEvent.GetGuildId();
 
-    for (auto const& calendarInvite : eventInviteeList)
+    if (CalendarInviteStore const* eventInviteeList = Trinity::Containers::MapGetValuePtr(_invites, calendarEvent.GetEventId()))
     {
-        ObjectGuid inviteeGuid = calendarInvite->GetInviteeGUID();
-        Player* invitee = ObjectAccessor::FindPlayer(inviteeGuid);
-
-        uint8 inviteeLevel = invitee ? invitee->GetLevel() : sCharacterCache->GetCharacterLevelByGuid(inviteeGuid);
-        ObjectGuid::LowType inviteeGuildId = invitee ? invitee->GetGuildId() : sCharacterCache->GetCharacterGuildIdByGuid(inviteeGuid);
-
-        WorldPackets::Calendar::CalendarEventInviteInfo inviteInfo;
-        inviteInfo.Guid = inviteeGuid;
-        inviteInfo.Level = inviteeLevel;
-        inviteInfo.Status = calendarInvite->GetStatus();
-        inviteInfo.Moderator = calendarInvite->GetRank();
-        inviteInfo.InviteType = calendarEvent.IsGuildEvent() && calendarEvent.GetGuildId() == inviteeGuildId;
-        inviteInfo.InviteID = calendarInvite->GetInviteId();
-        inviteInfo.ResponseTime = calendarInvite->GetResponseTime();
-        inviteInfo.Notes = calendarInvite->GetNote();
-
-        packet.Invites.push_back(inviteInfo);
+        for (CalendarInvite const* calendarInvite : *eventInviteeList)
+        {
+            ObjectGuid inviteeGuid = calendarInvite->GetInviteeGUID();
+            Player* invitee = ObjectAccessor::FindPlayer(inviteeGuid);
+
+            uint8 inviteeLevel = invitee ? invitee->GetLevel() : sCharacterCache->GetCharacterLevelByGuid(inviteeGuid);
+            ObjectGuid::LowType inviteeGuildId = invitee ? invitee->GetGuildId() : sCharacterCache->GetCharacterGuildIdByGuid(inviteeGuid);
+
+            WorldPackets::Calendar::CalendarEventInviteInfo inviteInfo;
+            inviteInfo.Guid = inviteeGuid;
+            inviteInfo.Level = inviteeLevel;
+            inviteInfo.Status = calendarInvite->GetStatus();
+            inviteInfo.Moderator = calendarInvite->GetRank();
+            inviteInfo.InviteType = calendarEvent.IsGuildEvent() && calendarEvent.GetGuildId() == inviteeGuildId;
+            inviteInfo.InviteID = calendarInvite->GetInviteId();
+            inviteInfo.ResponseTime.SetUtcTimeFromUnixTime(calendarInvite->GetResponseTime());
+            inviteInfo.ResponseTime += player->GetSession()->GetTimezoneOffset();
+            inviteInfo.Notes = calendarInvite->GetNote();
+
+            packet.Invites.push_back(inviteInfo);
+        }
     }
 
     player->SendDirectMessage(packet.Write());
 }
 
-void CalendarMgr::SendCalendarEventInviteRemoveAlert(ObjectGuid guid, CalendarEvent const& calendarEvent, CalendarInviteStatus status)
+void CalendarMgr::SendCalendarEventInviteRemoveAlert(ObjectGuid guid, CalendarEvent const& calendarEvent, CalendarInviteStatus status) const
 {
     if (Player* player = ObjectAccessor::FindConnectedPlayer(guid))
     {
         WorldPackets::Calendar::CalendarInviteRemovedAlert packet;
-        packet.Date = calendarEvent.GetDate();
+        packet.Date.SetUtcTimeFromUnixTime(calendarEvent.GetDate());
+        packet.Date += player->GetSession()->GetTimezoneOffset();
         packet.EventID = calendarEvent.GetEventId();
         packet.Flags = calendarEvent.GetFlags();
         packet.Status = status;
@@ -657,13 +708,13 @@ void CalendarMgr::SendCalendarEventInviteRemoveAlert(ObjectGuid guid, CalendarEv
     }
 }
 
-void CalendarMgr::SendCalendarClearPendingAction(ObjectGuid guid)
+void CalendarMgr::SendCalendarClearPendingAction(ObjectGuid guid) const
 {
     if (Player* player = ObjectAccessor::FindConnectedPlayer(guid))
         player->SendDirectMessage(WorldPackets::Calendar::CalendarClearPendingAction().Write());
 }
 
-void CalendarMgr::SendCalendarCommandResult(ObjectGuid guid, CalendarError err, char const* param /*= nullptr*/)
+void CalendarMgr::SendCalendarCommandResult(ObjectGuid guid, CalendarError err, char const* param /*= nullptr*/) const
 {
     if (Player* player = ObjectAccessor::FindConnectedPlayer(guid))
     {
@@ -686,17 +737,35 @@ void CalendarMgr::SendCalendarCommandResult(ObjectGuid guid, CalendarError err,
     }
 }
 
-void CalendarMgr::SendPacketToAllEventRelatives(WorldPacket const* packet, CalendarEvent const& calendarEvent)
+void CalendarMgr::SendPacketToAllEventRelatives(WorldPacket const* packet, CalendarEvent const& calendarEvent) const
 {
+    for (Player* player : GetAllEventRelatives(calendarEvent))
+        player->SendDirectMessage(packet);
+}
+
+std::vector<Player*> CalendarMgr::GetAllEventRelatives(CalendarEvent const& calendarEvent) const
+{
+    std::vector<Player*> relatedPlayers;
+
     // Send packet to all guild members
     if (calendarEvent.IsGuildEvent() || calendarEvent.IsGuildAnnouncement())
+    {
         if (Guild* guild = sGuildMgr->GetGuildById(calendarEvent.GetGuildId()))
-            guild->BroadcastPacket(packet);
+        {
+            auto memberCollector = [&](Player* player) { relatedPlayers.push_back(player); };
+            guild->BroadcastWorker(memberCollector);
+        }
+    }
 
     // Send packet to all invitees if event is non-guild, in other case only to non-guild invitees (packet was broadcasted for them)
-    CalendarInviteStore invites = _invites[calendarEvent.GetEventId()];
-    for (CalendarInviteStore::iterator itr = invites.begin(); itr != invites.end(); ++itr)
-        if (Player* player = ObjectAccessor::FindConnectedPlayer((*itr)->GetInviteeGUID()))
-            if (!calendarEvent.IsGuildEvent() || player->GetGuildId() != calendarEvent.GetGuildId())
-                player->SendDirectMessage(packet);
+    if (auto itr =_invites.find(calendarEvent.GetEventId()); itr != _invites.end())
+    {
+        CalendarInviteStore invites = itr->second;
+        for (CalendarInvite const* invite : invites)
+            if (Player* player = ObjectAccessor::FindConnectedPlayer(invite->GetInviteeGUID()))
+                if (!calendarEvent.IsGuildEvent() || player->GetGuildId() != calendarEvent.GetGuildId())
+                    relatedPlayers.push_back(player);
+    }
+
+    return relatedPlayers;
 }
diff --git a/src/server/game/Calendar/CalendarMgr.h b/src/server/game/Calendar/CalendarMgr.h
index e9119fc510f..7f0a33be1bc 100644
--- a/src/server/game/Calendar/CalendarMgr.h
+++ b/src/server/game/Calendar/CalendarMgr.h
@@ -26,6 +26,7 @@
 #include <set>
 #include <vector>
 
+class Player;
 class WorldPacket;
 
 enum CalendarMailAnswers
@@ -159,7 +160,13 @@ struct TC_GAME_API CalendarInvite
         CalendarInvite(uint64 inviteId, uint64 eventId, ObjectGuid invitee, ObjectGuid senderGUID, time_t responseTime,
             CalendarInviteStatus status, CalendarModerationRank rank, std::string note) :
             _inviteId(inviteId), _eventId(eventId), _invitee(invitee), _senderGUID(senderGUID), _responseTime(responseTime),
-            _status(status), _rank(rank), _note(note) { }
+            _status(status), _rank(rank), _note(std::move(note)) { }
+
+        CalendarInvite(CalendarInvite const&) = delete;
+        CalendarInvite(CalendarInvite&&) = delete;
+
+        CalendarInvite& operator=(CalendarInvite const&) = delete;
+        CalendarInvite& operator=(CalendarInvite&&) = delete;
 
         ~CalendarInvite();
 
@@ -218,10 +225,16 @@ struct TC_GAME_API CalendarEvent
         CalendarEvent(uint64 eventId, ObjectGuid ownerGUID, ObjectGuid::LowType guildId, CalendarEventType type, int32 textureId,
             time_t date, uint32 flags, std::string title, std::string description, time_t lockDate) :
             _eventId(eventId), _ownerGUID(ownerGUID), _eventGuildId(guildId), _eventType(type), _textureId(textureId),
-            _date(date), _flags(flags), _title(title), _description(description), _lockDate(lockDate) { }
+            _date(date), _flags(flags), _title(std::move(title)), _description(std::move(description)), _lockDate(lockDate) { }
 
         CalendarEvent() : _eventId(1), _ownerGUID(), _eventGuildId(UI64LIT(0)), _eventType(CALENDAR_TYPE_OTHER), _textureId(-1), _date(0),
-            _flags(0), _title(""), _description(""), _lockDate(0) { }
+            _flags(0), _title(), _description(), _lockDate(0) { }
+
+        CalendarEvent(CalendarEvent const&) = delete;
+        CalendarEvent(CalendarEvent&&) = delete;
+
+        CalendarEvent& operator=(CalendarEvent const&) = delete;
+        CalendarEvent& operator=(CalendarEvent&&) = delete;
 
         ~CalendarEvent();
 
@@ -263,7 +276,7 @@ struct TC_GAME_API CalendarEvent
         static bool IsGuildAnnouncement(uint32 flags) { return (flags & CALENDAR_FLAG_WITHOUT_INVITES) != 0; }
 
         std::string BuildCalendarMailSubject(ObjectGuid remover) const;
-        std::string BuildCalendarMailBody() const;
+        std::string BuildCalendarMailBody(Player const* invitee) const;
 
     private:
         uint64 _eventId;
@@ -296,20 +309,26 @@ class TC_GAME_API CalendarMgr
         uint64 _maxInviteId;
 
     public:
+        CalendarMgr(CalendarMgr const&) = delete;
+        CalendarMgr(CalendarMgr&&) = delete;
+
+        CalendarMgr& operator=(CalendarMgr const&) = delete;
+        CalendarMgr& operator=(CalendarMgr&&) = delete;
+
         static CalendarMgr* instance();
 
         void LoadFromDB();
 
         CalendarEvent* GetEvent(uint64 eventId) const;
         CalendarEventStore const& GetEvents() const { return _events; }
-        CalendarEventStore GetEventsCreatedBy(ObjectGuid guid, bool includeGuildEvents = false);
-        CalendarEventStore GetPlayerEvents(ObjectGuid guid);
-        CalendarEventStore GetGuildEvents(ObjectGuid::LowType guildId);
+        CalendarEventStore GetEventsCreatedBy(ObjectGuid guid, bool includeGuildEvents = false) const;
+        CalendarEventStore GetPlayerEvents(ObjectGuid guid) const;
+        CalendarEventStore GetGuildEvents(ObjectGuid::LowType guildId) const;
 
         CalendarInvite* GetInvite(uint64 inviteId) const;
         CalendarEventInviteStore const& GetInvites() const { return _invites; }
-        CalendarInviteStore const& GetEventInvites(uint64 eventId);
-        CalendarInviteStore GetPlayerInvites(ObjectGuid guid);
+        CalendarInviteStore GetEventInvites(uint64 eventId) const;
+        CalendarInviteStore GetPlayerInvites(ObjectGuid guid) const;
 
         void FreeEventId(uint64 id);
         uint64 GetFreeEventId();
@@ -332,19 +351,20 @@ class TC_GAME_API CalendarMgr
         void RemoveAllPlayerEventsAndInvites(ObjectGuid guid);
         void RemovePlayerGuildEventsAndSignups(ObjectGuid guid, ObjectGuid::LowType guildId);
 
-        void SendCalendarEvent(ObjectGuid guid, CalendarEvent const& calendarEvent, CalendarSendEventType sendType);
-        void SendCalendarEventInvite(CalendarInvite const& invite);
-        void SendCalendarEventInviteAlert(CalendarEvent const& calendarEvent, CalendarInvite const& invite);
-        void SendCalendarEventInviteRemove(CalendarEvent const& calendarEvent, CalendarInvite const& invite, uint32 flags);
-        void SendCalendarEventInviteRemoveAlert(ObjectGuid guid, CalendarEvent const& calendarEvent, CalendarInviteStatus status);
-        void SendCalendarEventUpdateAlert(CalendarEvent const& calendarEvent, time_t originalDate);
-        void SendCalendarEventStatus(CalendarEvent const& calendarEvent, CalendarInvite const& invite);
-        void SendCalendarEventRemovedAlert(CalendarEvent const& calendarEvent);
-        void SendCalendarEventModeratorStatusAlert(CalendarEvent const& calendarEvent, CalendarInvite const& invite);
-        void SendCalendarClearPendingAction(ObjectGuid guid);
-        void SendCalendarCommandResult(ObjectGuid guid, CalendarError err, char const* param = nullptr);
-
-        void SendPacketToAllEventRelatives(WorldPacket const* packet, CalendarEvent const& calendarEvent);
+        void SendCalendarEvent(ObjectGuid guid, CalendarEvent const& calendarEvent, CalendarSendEventType sendType) const;
+        void SendCalendarEventInvite(CalendarInvite const& invite) const;
+        void SendCalendarEventInviteAlert(CalendarEvent const& calendarEvent, CalendarInvite const& invite) const;
+        void SendCalendarEventInviteRemove(CalendarEvent const& calendarEvent, CalendarInvite const& invite, uint32 flags) const;
+        void SendCalendarEventInviteRemoveAlert(ObjectGuid guid, CalendarEvent const& calendarEvent, CalendarInviteStatus status) const;
+        void SendCalendarEventUpdateAlert(CalendarEvent const& calendarEvent, time_t originalDate) const;
+        void SendCalendarEventStatus(CalendarEvent const& calendarEvent, CalendarInvite const& invite) const;
+        void SendCalendarEventRemovedAlert(CalendarEvent const& calendarEvent) const;
+        void SendCalendarEventModeratorStatusAlert(CalendarEvent const& calendarEvent, CalendarInvite const& invite) const;
+        void SendCalendarClearPendingAction(ObjectGuid guid) const;
+        void SendCalendarCommandResult(ObjectGuid guid, CalendarError err, char const* param = nullptr) const;
+
+        void SendPacketToAllEventRelatives(WorldPacket const* packet, CalendarEvent const& calendarEvent) const;
+        std::vector<Player*> GetAllEventRelatives(CalendarEvent const& calendarEvent) const;
 };
 
 #define sCalendarMgr CalendarMgr::instance()
diff --git a/src/server/game/Conditions/ConditionMgr.cpp b/src/server/game/Conditions/ConditionMgr.cpp
index 0c59309bbb7..a7a74704a5d 100644
--- a/src/server/game/Conditions/ConditionMgr.cpp
+++ b/src/server/game/Conditions/ConditionMgr.cpp
@@ -19,12 +19,12 @@
 #include "AchievementMgr.h"
 #include "AreaTrigger.h"
 #include "AreaTriggerDataStore.h"
-#include "Battleground.h"
 #include "BattlePetMgr.h"
+#include "Battleground.h"
 #include "Containers.h"
 #include "ConversationDataStore.h"
-#include "DatabaseEnv.h"
 #include "DB2Stores.h"
+#include "DatabaseEnv.h"
 #include "GameEventMgr.h"
 #include "GameObject.h"
 #include "GameTime.h"
@@ -32,8 +32,8 @@
 #include "InstanceScenario.h"
 #include "InstanceScript.h"
 #include "Item.h"
-#include "LanguageMgr.h"
 #include "LFGMgr.h"
+#include "LanguageMgr.h"
 #include "Log.h"
 #include "LootMgr.h"
 #include "Map.h"
@@ -53,6 +53,7 @@
 #include "World.h"
 #include "WorldSession.h"
 #include "WorldStateMgr.h"
+#include "WowTime.h"
 #include <random>
 #include <sstream>
 
@@ -3239,15 +3240,18 @@ bool ConditionMgr::IsPlayerMeetingCondition(Player const* player, PlayerConditio
 
     if (condition->Time[0])
     {
-        ByteBuffer unpacker;
-        unpacker << condition->Time[0];
-        time_t from = unpacker.ReadPackedTime();
-        unpacker.rpos(0);
-        unpacker.wpos(0);
-        unpacker << condition->Time[1];
-        time_t to = unpacker.ReadPackedTime();
+        WowTime time0;
+        time0.SetPackedTime(condition->Time[0]);
+
+        if (condition->Time[1])
+        {
+            WowTime time1;
+            time1.SetPackedTime(condition->Time[1]);
 
-        if (GameTime::GetGameTime() < from || GameTime::GetGameTime() > to)
+            if (!GameTime::GetWowTime()->IsInRange(time0, time1))
+                return false;
+        }
+        else if (*GameTime::GetWowTime() != time0)
             return false;
     }
 
diff --git a/src/server/game/Entities/Player/Player.cpp b/src/server/game/Entities/Player/Player.cpp
index a93c6444d3b..531a103cc30 100644
--- a/src/server/game/Entities/Player/Player.cpp
+++ b/src/server/game/Entities/Player/Player.cpp
@@ -23354,8 +23354,8 @@ void Player::SendInitialPacketsBeforeAddToMap()
     static float const TimeSpeed = 0.01666667f;
     WorldPackets::Misc::LoginSetTimeSpeed loginSetTimeSpeed;
     loginSetTimeSpeed.NewSpeed = TimeSpeed;
-    loginSetTimeSpeed.GameTime = GameTime::GetGameTime();
-    loginSetTimeSpeed.ServerTime = GameTime::GetGameTime();
+    loginSetTimeSpeed.GameTime = *GameTime::GetWowTime();
+    loginSetTimeSpeed.ServerTime = *GameTime::GetWowTime();
     loginSetTimeSpeed.GameTimeHolidayOffset = 0; /// @todo
     loginSetTimeSpeed.ServerTimeHolidayOffset = 0; /// @todo
     SendDirectMessage(loginSetTimeSpeed.Write());
diff --git a/src/server/game/Guilds/Guild.cpp b/src/server/game/Guilds/Guild.cpp
index 035d8e00f3e..9874302350d 100644
--- a/src/server/game/Guilds/Guild.cpp
+++ b/src/server/game/Guilds/Guild.cpp
@@ -226,7 +226,7 @@ void Guild::NewsLogEntry::WritePacket(WorldPackets::Guild::GuildNews& newsPacket
     WorldPackets::Guild::GuildNewsEvent newsEvent;
     newsEvent.Id = int32(GetGUID());
     newsEvent.MemberGuid = GetPlayerGuid();
-    newsEvent.CompletedDate = uint32(GetTimestamp());
+    newsEvent.CompletedDate.SetUtcTimeFromUnixTime(GetTimestamp());
     newsEvent.Flags = int32(GetFlags());
     newsEvent.Type = int32(GetType());
 
@@ -1306,7 +1306,8 @@ void Guild::HandleRoster(WorldSession* session)
     WorldPackets::Guild::GuildRoster roster;
 
     roster.NumAccounts = int32(m_accountsNumber);
-    roster.CreateDate = uint32(m_createdDate);
+    roster.CreateDate.SetUtcTimeFromUnixTime(m_createdDate);
+    roster.CreateDate += session->GetTimezoneOffset();
     roster.GuildFlags = 0;
 
     roster.MemberData.reserve(m_members.size());
@@ -2183,7 +2184,10 @@ void Guild::SendNewsUpdate(WorldSession* session) const
     packet.NewsEvents.reserve(newsLog.size());
 
     for (NewsLogEntry const& newsLogEntry : newsLog)
+    {
         newsLogEntry.WritePacket(packet);
+        packet.NewsEvents.back().CompletedDate += session->GetTimezoneOffset();
+    }
 
     session->SendPacket(packet.Write());
 
@@ -2688,12 +2692,15 @@ void Guild::BroadcastPacket(WorldPacket const* packet) const
             player->SendDirectMessage(packet);
 }
 
-void Guild::BroadcastPacketIfTrackingAchievement(WorldPacket const* packet, uint32 criteriaId) const
+std::vector<Player*> Guild::GetMembersTrackingCriteria(uint32 criteriaId) const
 {
+    std::vector<Player*> members;
     for (auto const& [guid, member] : m_members)
         if (member.IsTrackingCriteriaId(criteriaId))
             if (Player* player = member.FindPlayer())
-                player->GetSession()->SendPacket(packet);
+                members.push_back(player);
+
+    return members;
 }
 
 void Guild::MassInviteToEvent(WorldSession* session, uint32 minLevel, uint32 maxLevel, GuildRankOrder minRank)
@@ -3599,10 +3606,16 @@ void Guild::AddGuildNews(uint8 type, ObjectGuid guid, uint32 flags, uint32 value
     NewsLogEntry& news = m_newsLog.AddEvent(trans, m_id, m_newsLog.GetNextGUID(), GuildNews(type), guid, flags, value);
     CharacterDatabase.CommitTransaction(trans);
 
-    WorldPackets::Guild::GuildNews newsPacket;
-    newsPacket.NewsEvents.reserve(1);
-    news.WritePacket(newsPacket);
-    BroadcastPacket(newsPacket.Write());
+    auto packetBuilder = [&](Player const* receiver)
+    {
+        WorldPackets::Guild::GuildNews newsPacket;
+        newsPacket.NewsEvents.reserve(1);
+        news.WritePacket(newsPacket);
+        newsPacket.NewsEvents.back().CompletedDate += receiver->GetSession()->GetTimezoneOffset();
+
+        receiver->SendDirectMessage(newsPacket.Write());
+    };
+    BroadcastWorker(packetBuilder);
 }
 
 bool Guild::HasAchieved(uint32 achievementId) const
@@ -3637,5 +3650,6 @@ void Guild::HandleNewsSetSticky(WorldSession* session, uint32 newsId, bool stick
     WorldPackets::Guild::GuildNews newsPacket;
     newsPacket.NewsEvents.reserve(1);
     itr->WritePacket(newsPacket);
+    newsPacket.NewsEvents.back().CompletedDate += session->GetTimezoneOffset();
     session->SendPacket(newsPacket.Write());
 }
diff --git a/src/server/game/Guilds/Guild.h b/src/server/game/Guilds/Guild.h
index bdbd05503c4..071e2c881da 100644
--- a/src/server/game/Guilds/Guild.h
+++ b/src/server/game/Guilds/Guild.h
@@ -810,7 +810,6 @@ class TC_GAME_API Guild
         void BroadcastAddonToGuild(WorldSession* session, bool officerOnly, std::string_view msg, std::string_view prefix, bool isLogged) const;
         void BroadcastPacketToRank(WorldPacket const* packet, GuildRankId rankId) const;
         void BroadcastPacket(WorldPacket const* packet) const;
-        void BroadcastPacketIfTrackingAchievement(WorldPacket const* packet, uint32 criteriaId) const;
 
         void MassInviteToEvent(WorldSession* session, uint32 minLevel, uint32 maxLevel, GuildRankOrder minRank);
 
@@ -831,6 +830,7 @@ class TC_GAME_API Guild
         bool IsMember(ObjectGuid guid) const;
         uint32 GetMembersCount() const { return uint32(m_members.size()); }
         uint64 GetMemberAvailableMoneyForRepairItems(ObjectGuid guid) const;
+        std::vector<Player*> GetMembersTrackingCriteria(uint32 criteriaId) const;
 
         // Bank
         void SwapItems(Player* player, uint8 tabId, uint8 slotId, uint8 destTabId, uint8 destSlotId, uint32 splitedAmount);
diff --git a/src/server/game/Handlers/AuthHandler.cpp b/src/server/game/Handlers/AuthHandler.cpp
index 7be557d368b..13db0718450 100644
--- a/src/server/game/Handlers/AuthHandler.cpp
+++ b/src/server/game/Handlers/AuthHandler.cpp
@@ -26,6 +26,7 @@
 #include "RBAC.h"
 #include "Realm.h"
 #include "SystemPackets.h"
+#include "Timezone.h"
 #include "World.h"
 
 void WorldSession::SendAuthResponse(uint32 code, bool queued, uint32 queuePos)
@@ -89,12 +90,14 @@ void WorldSession::SendClientCacheVersion(uint32 version)
 
 void WorldSession::SendSetTimeZoneInformation()
 {
-    /// @todo: replace dummy values
-    WorldPackets::System::SetTimeZoneInformation packet;
-    packet.ServerTimeTZ = "Europe/Paris";
-    packet.GameTimeTZ = "Europe/Paris";
-    packet.ServerRegionalTZ = "Europe/Paris";
+    Minutes timezoneOffset = Trinity::Timezone::GetSystemZoneOffset(false);
+    std::string realTimezone = Trinity::Timezone::GetSystemZoneName();
+    std::string_view clientSupportedTZ = Trinity::Timezone::FindClosestClientSupportedTimezone(realTimezone, timezoneOffset);
 
+    WorldPackets::System::SetTimeZoneInformation packet;
+    packet.ServerTimeTZ = clientSupportedTZ;
+    packet.GameTimeTZ = clientSupportedTZ;
+    packet.ServerRegionalTZ = clientSupportedTZ;
     SendPacket(packet.Write());
 }
 
diff --git a/src/server/game/Handlers/CalendarHandler.cpp b/src/server/game/Handlers/CalendarHandler.cpp
index 209babfec10..ab512f54eec 100644
--- a/src/server/game/Handlers/CalendarHandler.cpp
+++ b/src/server/game/Handlers/CalendarHandler.cpp
@@ -39,7 +39,6 @@ Copied events should probably have a new owner
 #include "CalendarPackets.h"
 #include "CharacterCache.h"
 #include "DatabaseEnv.h"
-#include "DB2Stores.h"
 #include "GameTime.h"
 #include "Guild.h"
 #include "GuildMgr.h"
@@ -49,16 +48,14 @@ Copied events should probably have a new owner
 #include "ObjectMgr.h"
 #include "Player.h"
 #include "SocialMgr.h"
-#include "Util.h"
 #include "World.h"
 
 void WorldSession::HandleCalendarGetCalendar(WorldPackets::Calendar::CalendarGetCalendar& /*calendarGetCalendar*/)
 {
     ObjectGuid guid = _player->GetGUID();
-    time_t currTime = GameTime::GetGameTime();
 
     WorldPackets::Calendar::CalendarSendCalendar packet;
-    packet.ServerTime = currTime;
+    packet.ServerTime = *GameTime::GetWowTime();
 
     CalendarInviteStore playerInvites = sCalendarMgr->GetPlayerInvites(guid);
     for (CalendarInvite const* invite : playerInvites)
@@ -78,7 +75,8 @@ void WorldSession::HandleCalendarGetCalendar(WorldPackets::Calendar::CalendarGet
     {
         WorldPackets::Calendar::CalendarSendCalendarEventInfo& eventInfo = packet.Events.emplace_back();
         eventInfo.EventID = event->GetEventId();
-        eventInfo.Date = event->GetDate();
+        eventInfo.Date.SetUtcTimeFromUnixTime(event->GetDate());
+        eventInfo.Date += GetTimezoneOffset();
         eventInfo.EventClubID = event->GetGuildId();
         eventInfo.EventName = event->GetTitle();
         eventInfo.EventType = event->GetType();
@@ -117,11 +115,10 @@ void WorldSession::HandleCalendarAddEvent(WorldPackets::Calendar::CalendarAddEve
 {
     ObjectGuid guid = _player->GetGUID();
 
-    calendarAddEvent.EventInfo.Time = uint32(LocalTimeToUTCTime(calendarAddEvent.EventInfo.Time));
+    calendarAddEvent.EventInfo.Time -= GetTimezoneOffset();
 
     // prevent events in the past
-    // To Do: properly handle timezones and remove the "- time_t(86400L)" hack
-    if (calendarAddEvent.EventInfo.Time < (GameTime::GetGameTime() - time_t(86400L)))
+    if (calendarAddEvent.EventInfo.Time < *GameTime::GetUtcWowTime())
     {
         sCalendarMgr->SendCalendarCommandResult(guid, CALENDAR_ERROR_EVENT_PASSED);
         return;
@@ -163,7 +160,7 @@ void WorldSession::HandleCalendarAddEvent(WorldPackets::Calendar::CalendarAddEve
     SetCalendarEventCreationCooldown(GameTime::GetGameTime() + CALENDAR_CREATE_EVENT_COOLDOWN);
 
     CalendarEvent* calendarEvent = new CalendarEvent(sCalendarMgr->GetFreeEventId(), guid, UI64LIT(0), CalendarEventType(calendarAddEvent.EventInfo.EventType), calendarAddEvent.EventInfo.TextureID,
-        calendarAddEvent.EventInfo.Time, calendarAddEvent.EventInfo.Flags, calendarAddEvent.EventInfo.Title, calendarAddEvent.EventInfo.Description, time_t(0));
+        calendarAddEvent.EventInfo.Time.GetUnixTimeFromUtcTime(), calendarAddEvent.EventInfo.Flags, calendarAddEvent.EventInfo.Title, calendarAddEvent.EventInfo.Description, time_t(0));
 
     if (calendarEvent->IsGuildEvent() || calendarEvent->IsGuildAnnouncement())
         calendarEvent->SetGuildId(_player->GetGuildId());
@@ -201,11 +198,10 @@ void WorldSession::HandleCalendarUpdateEvent(WorldPackets::Calendar::CalendarUpd
     ObjectGuid guid = _player->GetGUID();
     time_t oldEventTime = time_t(0);
 
-    calendarUpdateEvent.EventInfo.Time = uint32(LocalTimeToUTCTime(calendarUpdateEvent.EventInfo.Time));
+    calendarUpdateEvent.EventInfo.Time -= GetTimezoneOffset();
 
     // prevent events in the past
-    // To Do: properly handle timezones and remove the "- time_t(86400L)" hack
-    if (calendarUpdateEvent.EventInfo.Time < (GameTime::GetGameTime() - time_t(86400L)))
+    if (calendarUpdateEvent.EventInfo.Time < *GameTime::GetUtcWowTime())
         return;
 
     if (CalendarEvent* calendarEvent = sCalendarMgr->GetEvent(calendarUpdateEvent.EventInfo.EventID))
@@ -214,7 +210,7 @@ void WorldSession::HandleCalendarUpdateEvent(WorldPackets::Calendar::CalendarUpd
 
         calendarEvent->SetType(CalendarEventType(calendarUpdateEvent.EventInfo.EventType));
         calendarEvent->SetFlags(calendarUpdateEvent.EventInfo.Flags);
-        calendarEvent->SetDate(calendarUpdateEvent.EventInfo.Time);
+        calendarEvent->SetDate(calendarUpdateEvent.EventInfo.Time.GetUnixTimeFromUtcTime());
         calendarEvent->SetTextureId(calendarUpdateEvent.EventInfo.TextureID);
         calendarEvent->SetTitle(calendarUpdateEvent.EventInfo.Title);
         calendarEvent->SetDescription(calendarUpdateEvent.EventInfo.Description);
@@ -236,11 +232,10 @@ void WorldSession::HandleCalendarCopyEvent(WorldPackets::Calendar::CalendarCopyE
 {
     ObjectGuid guid = _player->GetGUID();
 
-    calendarCopyEvent.Date = uint32(LocalTimeToUTCTime(calendarCopyEvent.Date));
+    calendarCopyEvent.Date -= GetTimezoneOffset();
 
     // prevent events in the past
-    // To Do: properly handle timezones and remove the "- time_t(86400L)" hack
-    if (calendarCopyEvent.Date < (GameTime::GetGameTime() - time_t(86400L)))
+    if (calendarCopyEvent.Date < *GameTime::GetUtcWowTime())
     {
         sCalendarMgr->SendCalendarCommandResult(guid, CALENDAR_ERROR_EVENT_PASSED);
         return;
@@ -292,7 +287,7 @@ void WorldSession::HandleCalendarCopyEvent(WorldPackets::Calendar::CalendarCopyE
         SetCalendarEventCreationCooldown(GameTime::GetGameTime() + CALENDAR_CREATE_EVENT_COOLDOWN);
 
         CalendarEvent* newEvent = new CalendarEvent(*oldEvent, sCalendarMgr->GetFreeEventId());
-        newEvent->SetDate(calendarCopyEvent.Date);
+        newEvent->SetDate(calendarCopyEvent.Date.GetUnixTimeFromUtcTime());
         sCalendarMgr->AddEvent(newEvent, CALENDAR_SENDTYPE_COPY);
 
         CalendarInviteStore invites = sCalendarMgr->GetEventInvites(calendarCopyEvent.EventID);
@@ -550,7 +545,7 @@ void WorldSession::HandleSetSavedInstanceExtend(WorldPackets::Calendar::SetSaved
         return;
 
     WorldPackets::Calendar::CalendarRaidLockoutUpdated calendarRaidLockoutUpdated;
-    calendarRaidLockoutUpdated.ServerTime = GameTime::GetGameTime();
+    calendarRaidLockoutUpdated.ServerTime = *GameTime::GetWowTime();
     calendarRaidLockoutUpdated.MapID = setSavedInstanceExtend.MapID;
     calendarRaidLockoutUpdated.DifficultyID = setSavedInstanceExtend.DifficultyID;
     calendarRaidLockoutUpdated.OldTimeRemaining = std::max(std::chrono::duration_cast<Seconds>(expiryTimes.first - GameTime::GetSystemTime()).count(), SI64LIT(0));
diff --git a/src/server/game/Quests/QuestObjectiveCriteriaMgr.cpp b/src/server/game/Quests/QuestObjectiveCriteriaMgr.cpp
index a72c213a042..798e90e6b26 100644
--- a/src/server/game/Quests/QuestObjectiveCriteriaMgr.cpp
+++ b/src/server/game/Quests/QuestObjectiveCriteriaMgr.cpp
@@ -25,6 +25,7 @@
 #include "Map.h"
 #include "ObjectMgr.h"
 #include "Player.h"
+#include "WorldSession.h"
 
 QuestObjectiveCriteriaMgr::QuestObjectiveCriteriaMgr(Player* owner) : _owner(owner)
 {
@@ -187,7 +188,8 @@ void QuestObjectiveCriteriaMgr::SendAllData(Player const* /*receiver*/) const
         criteriaUpdate.PlayerGUID = _owner->GetGUID();
         criteriaUpdate.Flags = 0;
 
-        criteriaUpdate.CurrentTime = criteriaProgres.second.Date;
+        criteriaUpdate.CurrentTime.SetUtcTimeFromUnixTime(criteriaProgres.second.Date);
+        criteriaUpdate.CurrentTime += _owner->GetSession()->GetTimezoneOffset();
         criteriaUpdate.CreationTime = 0;
 
         SendPacket(criteriaUpdate.Write());
@@ -222,7 +224,8 @@ void QuestObjectiveCriteriaMgr::SendCriteriaUpdate(Criteria const* criteria, Cri
     if (criteria->Entry->StartTimer)
         criteriaUpdate.Flags = timedCompleted ? 1 : 0; // 1 is for keeping the counter at 0 in client
 
-    criteriaUpdate.CurrentTime = progress->Date;
+    criteriaUpdate.CurrentTime.SetUtcTimeFromUnixTime(progress->Date);
+    criteriaUpdate.CurrentTime += _owner->GetSession()->GetTimezoneOffset();
     criteriaUpdate.ElapsedTime = timeElapsed;
     criteriaUpdate.CreationTime = 0;
 
diff --git a/src/server/game/Scenarios/Scenario.cpp b/src/server/game/Scenarios/Scenario.cpp
index 3366781ba39..ce994618d62 100644
--- a/src/server/game/Scenarios/Scenario.cpp
+++ b/src/server/game/Scenarios/Scenario.cpp
@@ -23,6 +23,7 @@
 #include "Player.h"
 #include "ScenarioMgr.h"
 #include "ScenarioPackets.h"
+#include "WorldSession.h"
 
 Scenario::Scenario(Map* map, ScenarioData const* scenarioData) : _map(map), _data(scenarioData),
     _guid(ObjectGuid::Create<HighGuid::Scenario>(map->GetId(), scenarioData->Entry->ID, map->GenerateLowGuid<HighGuid::Scenario>())),
@@ -100,9 +101,12 @@ void Scenario::SetStep(ScenarioStepEntry const* step)
                 player->StartCriteria(CriteriaStartEvent::BeginScenarioStep, step->ID);
     }
 
-    WorldPackets::Scenario::ScenarioState scenarioState;
-    BuildScenarioState(&scenarioState);
-    SendPacket(scenarioState.Write());
+    DoForAllPlayers([&](Player const* receiver)
+    {
+        WorldPackets::Scenario::ScenarioState scenarioState;
+        BuildScenarioStateFor(receiver, &scenarioState);
+        receiver->SendDirectMessage(scenarioState.Write());
+    });
 }
 
 void Scenario::OnPlayerEnter(Player* player)
@@ -117,7 +121,7 @@ void Scenario::OnPlayerExit(Player* player)
     SendBootPlayer(player);
 }
 
-bool Scenario::IsComplete()
+bool Scenario::IsComplete() const
 {
     for (std::pair<uint8 const, ScenarioStepEntry const*> const& scenarioStep : _data->Steps)
     {
@@ -136,7 +140,7 @@ ScenarioEntry const* Scenario::GetEntry() const
     return _data->Entry;
 }
 
-ScenarioStepState Scenario::GetStepState(ScenarioStepEntry const* step)
+ScenarioStepState Scenario::GetStepState(ScenarioStepEntry const* step) const
 {
     auto itr = _stepStates.find(step);
     if (itr == _stepStates.end())
@@ -145,20 +149,24 @@ ScenarioStepState Scenario::GetStepState(ScenarioStepEntry const* step)
     return itr->second;
 }
 
-void Scenario::SendCriteriaUpdate(Criteria const * criteria, CriteriaProgress const * progress, Seconds timeElapsed, bool timedCompleted) const
+void Scenario::SendCriteriaUpdate(Criteria const* criteria, CriteriaProgress const* progress, Seconds timeElapsed, bool timedCompleted) const
 {
-    WorldPackets::Scenario::ScenarioProgressUpdate progressUpdate;
-    progressUpdate.CriteriaProgress.Id = criteria->ID;
-    progressUpdate.CriteriaProgress.Quantity = progress->Counter;
-    progressUpdate.CriteriaProgress.Player = progress->PlayerGUID;
-    progressUpdate.CriteriaProgress.Date = progress->Date;
-    if (criteria->Entry->StartTimer)
-        progressUpdate.CriteriaProgress.Flags = timedCompleted ? 1 : 0;
-
-    progressUpdate.CriteriaProgress.TimeFromStart = timeElapsed;
-    progressUpdate.CriteriaProgress.TimeFromCreate = Seconds::zero();
-
-    SendPacket(progressUpdate.Write());
+    DoForAllPlayers([=](Player const* receiver)
+    {
+        WorldPackets::Scenario::ScenarioProgressUpdate progressUpdate;
+        progressUpdate.CriteriaProgress.Id = criteria->ID;
+        progressUpdate.CriteriaProgress.Quantity = progress->Counter;
+        progressUpdate.CriteriaProgress.Player = progress->PlayerGUID;
+        progressUpdate.CriteriaProgress.Date.SetUtcTimeFromUnixTime(progress->Date);
+        progressUpdate.CriteriaProgress.Date += receiver->GetSession()->GetTimezoneOffset();
+        if (criteria->Entry->StartTimer)
+            progressUpdate.CriteriaProgress.Flags = timedCompleted ? 1 : 0;
+
+        progressUpdate.CriteriaProgress.TimeFromStart = timeElapsed;
+        progressUpdate.CriteriaProgress.TimeFromCreate = Seconds::zero();
+
+        receiver->SendDirectMessage(progressUpdate.Write());
+    });
 }
 
 bool Scenario::CanUpdateCriteriaTree(Criteria const * /*criteria*/, CriteriaTree const * tree, Player * /*referencePlayer*/) const
@@ -220,20 +228,28 @@ bool Scenario::IsCompletedStep(ScenarioStepEntry const* step)
     return IsCompletedCriteriaTree(tree);
 }
 
-void Scenario::SendPacket(WorldPacket const* data) const
+void Scenario::DoForAllPlayers(std::function<void(Player*)> const& worker) const
 {
     for (ObjectGuid guid : _players)
         if (Player* player = ObjectAccessor::GetPlayer(_map, guid))
-            player->SendDirectMessage(data);
+            worker(player);
 }
 
-void Scenario::BuildScenarioState(WorldPackets::Scenario::ScenarioState* scenarioState)
+void Scenario::SendPacket(WorldPacket const* data) const
+{
+    DoForAllPlayers([data](Player const* player)
+    {
+        player->SendDirectMessage(data);
+    });
+}
+
+void Scenario::BuildScenarioStateFor(Player const* player, WorldPackets::Scenario::ScenarioState* scenarioState) const
 {
     scenarioState->ScenarioGUID = _guid;
     scenarioState->ScenarioID = _data->Entry->ID;
     if (ScenarioStepEntry const* step = GetStep())
         scenarioState->CurrentStep = step->ID;
-    scenarioState->CriteriaProgress = GetCriteriasProgress();
+    scenarioState->CriteriaProgress = GetCriteriasProgressFor(player);
     scenarioState->BonusObjectives = GetBonusObjectivesData();
     // Don't know exactly what this is for, but seems to contain list of scenario steps that we're either on or that are completed
     for (std::pair<ScenarioStepEntry const* const, ScenarioStepState> const& state : _stepStates)
@@ -288,14 +304,14 @@ ScenarioStepEntry const* Scenario::GetLastStep() const
     return lastStep;
 }
 
-void Scenario::SendScenarioState(Player* player)
+void Scenario::SendScenarioState(Player const* player) const
 {
     WorldPackets::Scenario::ScenarioState scenarioState;
-    BuildScenarioState(&scenarioState);
+    BuildScenarioStateFor(player, &scenarioState);
     player->SendDirectMessage(scenarioState.Write());
 }
 
-std::vector<WorldPackets::Scenario::BonusObjectiveData> Scenario::GetBonusObjectivesData()
+std::vector<WorldPackets::Scenario::BonusObjectiveData> Scenario::GetBonusObjectivesData() const
 {
     std::vector<WorldPackets::Scenario::BonusObjectiveData> bonusObjectivesData;
     for (std::pair<uint8 const, ScenarioStepEntry const*> const& scenarioStep : _data->Steps)
@@ -315,21 +331,18 @@ std::vector<WorldPackets::Scenario::BonusObjectiveData> Scenario::GetBonusObject
     return bonusObjectivesData;
 }
 
-std::vector<WorldPackets::Achievement::CriteriaProgress> Scenario::GetCriteriasProgress()
+std::vector<WorldPackets::Achievement::CriteriaProgress> Scenario::GetCriteriasProgressFor(Player const* player) const
 {
     std::vector<WorldPackets::Achievement::CriteriaProgress> criteriasProgress;
 
-    if (!_criteriaProgress.empty())
+    for (auto const& [criteriaId, progress] : _criteriaProgress)
     {
-        for (std::pair<uint32 const, CriteriaProgress> const& progressPair : _criteriaProgress)
-        {
-            WorldPackets::Achievement::CriteriaProgress criteriaProgress;
-            criteriaProgress.Id = progressPair.first;
-            criteriaProgress.Quantity = progressPair.second.Counter;
-            criteriaProgress.Date = progressPair.second.Date;
-            criteriaProgress.Player = progressPair.second.PlayerGUID;
-            criteriasProgress.push_back(criteriaProgress);
-        }
+        WorldPackets::Achievement::CriteriaProgress& criteriaProgress = criteriasProgress.emplace_back();
+        criteriaProgress.Id = criteriaId;
+        criteriaProgress.Quantity = progress.Counter;
+        criteriaProgress.Date.SetUtcTimeFromUnixTime(progress.Date);
+        criteriaProgress.Date += player->GetSession()->GetTimezoneOffset();
+        criteriaProgress.Player = progress.PlayerGUID;
     }
 
     return criteriasProgress;
@@ -340,7 +353,7 @@ CriteriaList const& Scenario::GetCriteriaByType(CriteriaType type, uint32 /*asse
     return sCriteriaMgr->GetScenarioCriteriaByTypeAndScenario(type, _data->Entry->ID);
 }
 
-void Scenario::SendBootPlayer(Player* player)
+void Scenario::SendBootPlayer(Player const* player) const
 {
     WorldPackets::Scenario::ScenarioVacate scenarioBoot;
     scenarioBoot.ScenarioGUID = _guid;
diff --git a/src/server/game/Scenarios/Scenario.h b/src/server/game/Scenarios/Scenario.h
index 7c632eca0cb..d70331adbdc 100644
--- a/src/server/game/Scenarios/Scenario.h
+++ b/src/server/game/Scenarios/Scenario.h
@@ -65,17 +65,17 @@ class TC_GAME_API Scenario : public CriteriaHandler
         virtual void OnPlayerExit(Player* player);
         virtual void Update(uint32 /*diff*/) { }
 
-        bool IsComplete();
+        bool IsComplete() const;
         bool IsCompletedStep(ScenarioStepEntry const* step);
         void SetStepState(ScenarioStepEntry const* step, ScenarioStepState state) { _stepStates[step] = state; }
         ScenarioEntry const* GetEntry() const;
-        ScenarioStepState GetStepState(ScenarioStepEntry const* step);
+        ScenarioStepState GetStepState(ScenarioStepEntry const* step) const;
         ScenarioStepEntry const* GetStep() const { return _currentstep; }
         ScenarioStepEntry const* GetFirstStep() const;
         ScenarioStepEntry const* GetLastStep() const;
 
-        void SendScenarioState(Player* player);
-        void SendBootPlayer(Player* player);
+        void SendScenarioState(Player const* player) const;
+        void SendBootPlayer(Player const* player) const;
 
     protected:
         Map const* _map;
@@ -89,14 +89,15 @@ class TC_GAME_API Scenario : public CriteriaHandler
         void CompletedCriteriaTree(CriteriaTree const* tree, Player* referencePlayer) override;
         void AfterCriteriaTreeUpdate(CriteriaTree const* /*tree*/, Player* /*referencePlayer*/) override { }
 
+        void DoForAllPlayers(std::function<void(Player*)> const& worker) const;
         void SendPacket(WorldPacket const* data) const override;
 
         void SendAllData(Player const* /*receiver*/) const override { }
 
-        void BuildScenarioState(WorldPackets::Scenario::ScenarioState* scenarioState);
+        void BuildScenarioStateFor(Player const* player, WorldPackets::Scenario::ScenarioState* scenarioState) const;
 
-        std::vector<WorldPackets::Scenario::BonusObjectiveData> GetBonusObjectivesData();
-        std::vector<WorldPackets::Achievement::CriteriaProgress> GetCriteriasProgress();
+        std::vector<WorldPackets::Scenario::BonusObjectiveData> GetBonusObjectivesData() const;
+        std::vector<WorldPackets::Achievement::CriteriaProgress> GetCriteriasProgressFor(Player const* player) const;
 
         CriteriaList const& GetCriteriaByType(CriteriaType type, uint32 asset) const override;
         ScenarioData const* _data;
diff --git a/src/server/game/Server/Packets/AchievementPackets.cpp b/src/server/game/Server/Packets/AchievementPackets.cpp
index d158db68e60..cf8111ba8b4 100644
--- a/src/server/game/Server/Packets/AchievementPackets.cpp
+++ b/src/server/game/Server/Packets/AchievementPackets.cpp
@@ -17,24 +17,26 @@
 
 #include "AchievementPackets.h"
 
-ByteBuffer& operator<<(ByteBuffer& data, WorldPackets::Achievement::EarnedAchievement const& earned)
+namespace WorldPackets::Achievement
+{
+ByteBuffer& operator<<(ByteBuffer& data, EarnedAchievement const& earned)
 {
     data << uint32(earned.Id);
-    data.AppendPackedTime(earned.Date);
+    data << earned.Date;
     data << earned.Owner;
     data << uint32(earned.VirtualRealmAddress);
     data << uint32(earned.NativeRealmAddress);
     return data;
 }
 
-ByteBuffer& operator<<(ByteBuffer& data, WorldPackets::Achievement::CriteriaProgress const& criteria)
+ByteBuffer& operator<<(ByteBuffer& data, CriteriaProgress const& criteria)
 {
     data << uint32(criteria.Id);
     data << uint64(criteria.Quantity);
     data << criteria.Player;
     data << uint32(criteria.Unused_10_1_5);
     data << uint32(criteria.Flags);
-    data.AppendPackedTime(criteria.Date);
+    data << criteria.Date;
     data << criteria.TimeFromStart;
     data << criteria.TimeFromCreate;
     data.WriteBit(criteria.RafAcceptanceID.has_value());
@@ -46,37 +48,37 @@ ByteBuffer& operator<<(ByteBuffer& data, WorldPackets::Achievement::CriteriaProg
     return data;
 }
 
-ByteBuffer& operator<<(ByteBuffer& data, WorldPackets::Achievement::AllAchievements const& allAchievements)
+ByteBuffer& operator<<(ByteBuffer& data, AllAchievements const& allAchievements)
 {
     data << uint32(allAchievements.Earned.size());
     data << uint32(allAchievements.Progress.size());
 
-    for (WorldPackets::Achievement::EarnedAchievement const& earned : allAchievements.Earned)
+    for (EarnedAchievement const& earned : allAchievements.Earned)
         data << earned;
 
-    for (WorldPackets::Achievement::CriteriaProgress const& progress : allAchievements.Progress)
+    for (CriteriaProgress const& progress : allAchievements.Progress)
         data << progress;
 
     return data;
 }
 
-WorldPacket const* WorldPackets::Achievement::AllAchievementData::Write()
+WorldPacket const* AllAchievementData::Write()
 {
     _worldPacket << Data;
 
     return &_worldPacket;
 }
 
-WorldPacket const* WorldPackets::Achievement::AllAccountCriteria::Write()
+WorldPacket const* AllAccountCriteria::Write()
 {
     _worldPacket << uint32(Progress.size());
-    for (WorldPackets::Achievement::CriteriaProgress const& progress : Progress)
+    for (CriteriaProgress const& progress : Progress)
         _worldPacket << progress;
 
     return &_worldPacket;
 }
 
-WorldPacket const* WorldPackets::Achievement::RespondInspectAchievements::Write()
+WorldPacket const* RespondInspectAchievements::Write()
 {
     _worldPacket << Player;
     _worldPacket << Data;
@@ -84,14 +86,14 @@ WorldPacket const* WorldPackets::Achievement::RespondInspectAchievements::Write(
     return &_worldPacket;
 }
 
-WorldPacket const* WorldPackets::Achievement::CriteriaUpdate::Write()
+WorldPacket const* CriteriaUpdate::Write()
 {
     _worldPacket << uint32(CriteriaID);
     _worldPacket << uint64(Quantity);
     _worldPacket << PlayerGUID;
     _worldPacket << uint32(Unused_10_1_5);
     _worldPacket << uint32(Flags);
-    _worldPacket.AppendPackedTime(CurrentTime);
+    _worldPacket << CurrentTime;
     _worldPacket << ElapsedTime;
     _worldPacket << CreationTime;
     _worldPacket.WriteBit(RafAcceptanceID.has_value());
@@ -103,21 +105,21 @@ WorldPacket const* WorldPackets::Achievement::CriteriaUpdate::Write()
     return &_worldPacket;
 }
 
-WorldPacket const* WorldPackets::Achievement::AccountCriteriaUpdate::Write()
+WorldPacket const* AccountCriteriaUpdate::Write()
 {
     _worldPacket << Progress;
 
     return &_worldPacket;
 }
 
-WorldPacket const* WorldPackets::Achievement::CriteriaDeleted::Write()
+WorldPacket const* CriteriaDeleted::Write()
 {
     _worldPacket << uint32(CriteriaID);
 
     return &_worldPacket;
 }
 
-WorldPacket const* WorldPackets::Achievement::AchievementDeleted::Write()
+WorldPacket const* AchievementDeleted::Write()
 {
     _worldPacket << uint32(AchievementID);
     _worldPacket << uint32(Immunities);
@@ -125,12 +127,12 @@ WorldPacket const* WorldPackets::Achievement::AchievementDeleted::Write()
     return &_worldPacket;
 }
 
-WorldPacket const* WorldPackets::Achievement::AchievementEarned::Write()
+WorldPacket const* AchievementEarned::Write()
 {
     _worldPacket << Sender;
     _worldPacket << Earner;
     _worldPacket << uint32(AchievementID);
-    _worldPacket.AppendPackedTime(Time);
+    _worldPacket << Time;
     _worldPacket << uint32(EarnerNativeRealm);
     _worldPacket << uint32(EarnerVirtualRealm);
     _worldPacket.WriteBit(Initial);
@@ -139,7 +141,7 @@ WorldPacket const* WorldPackets::Achievement::AchievementEarned::Write()
     return &_worldPacket;
 }
 
-WorldPacket const* WorldPackets::Achievement::BroadcastAchievement::Write()
+WorldPacket const* BroadcastAchievement::Write()
 {
     _worldPacket.WriteBits(Name.length(), 7);
     _worldPacket.WriteBit(GuildAchievement);
@@ -150,7 +152,7 @@ WorldPacket const* WorldPackets::Achievement::BroadcastAchievement::Write()
     return &_worldPacket;
 }
 
-WorldPacket const* WorldPackets::Achievement::GuildCriteriaUpdate::Write()
+WorldPacket const* GuildCriteriaUpdate::Write()
 {
     _worldPacket << uint32(Progress.size());
 
@@ -159,8 +161,7 @@ WorldPacket const* WorldPackets::Achievement::GuildCriteriaUpdate::Write()
         _worldPacket << int32(progress.CriteriaID);
         _worldPacket << progress.DateCreated;
         _worldPacket << progress.DateStarted;
-        _worldPacket.AppendPackedTime(progress.DateUpdated);
-        _worldPacket << uint32(0); // this is a hack. this is a packed time written as int64 (progress.DateUpdated)
+        _worldPacket << int64(progress.DateUpdated.GetPackedTime());
         _worldPacket << uint64(progress.Quantity);
         _worldPacket << progress.PlayerGUID;
         _worldPacket << int32(progress.Unused_10_1_5);
@@ -170,7 +171,7 @@ WorldPacket const* WorldPackets::Achievement::GuildCriteriaUpdate::Write()
     return &_worldPacket;
 }
 
-WorldPacket const* WorldPackets::Achievement::GuildCriteriaDeleted::Write()
+WorldPacket const* GuildCriteriaDeleted::Write()
 {
     _worldPacket << GuildGUID;
     _worldPacket << int32(CriteriaID);
@@ -178,30 +179,30 @@ WorldPacket const* WorldPackets::Achievement::GuildCriteriaDeleted::Write()
     return &_worldPacket;
 }
 
-void WorldPackets::Achievement::GuildSetFocusedAchievement::Read()
+void GuildSetFocusedAchievement::Read()
 {
     _worldPacket >> AchievementID;
 }
 
-WorldPacket const* WorldPackets::Achievement::GuildAchievementDeleted::Write()
+WorldPacket const* GuildAchievementDeleted::Write()
 {
     _worldPacket << GuildGUID;
     _worldPacket << uint32(AchievementID);
-    _worldPacket.AppendPackedTime(TimeDeleted);
+    _worldPacket << TimeDeleted;
 
     return &_worldPacket;
 }
 
-WorldPacket const* WorldPackets::Achievement::GuildAchievementEarned::Write()
+WorldPacket const* GuildAchievementEarned::Write()
 {
     _worldPacket << GuildGUID;
     _worldPacket << uint32(AchievementID);
-    _worldPacket.AppendPackedTime(TimeEarned);
+    _worldPacket << TimeEarned;
 
     return &_worldPacket;
 }
 
-WorldPacket const* WorldPackets::Achievement::AllGuildAchievements::Write()
+WorldPacket const* AllGuildAchievements::Write()
 {
     _worldPacket << uint32(Earned.size());
 
@@ -211,20 +212,20 @@ WorldPacket const* WorldPackets::Achievement::AllGuildAchievements::Write()
     return &_worldPacket;
 }
 
-void WorldPackets::Achievement::GuildGetAchievementMembers::Read()
+void GuildGetAchievementMembers::Read()
 {
     _worldPacket >> PlayerGUID;
     _worldPacket >> GuildGUID;
     _worldPacket >> AchievementID;
 }
 
-ByteBuffer& operator<<(ByteBuffer& data, WorldPackets::Achievement::GuildAchievementMember const& guildAchievementMember)
+ByteBuffer& operator<<(ByteBuffer& data, GuildAchievementMember const& guildAchievementMember)
 {
     data << guildAchievementMember.MemberGUID;
     return data;
 }
 
-WorldPacket const* WorldPackets::Achievement::GuildAchievementMembers::Write()
+WorldPacket const* GuildAchievementMembers::Write()
 {
     _worldPacket << GuildGUID;
     _worldPacket << int32(AchievementID);
@@ -234,3 +235,4 @@ WorldPacket const* WorldPackets::Achievement::GuildAchievementMembers::Write()
 
     return &_worldPacket;
 }
+}
diff --git a/src/server/game/Server/Packets/AchievementPackets.h b/src/server/game/Server/Packets/AchievementPackets.h
index 39aa72aba16..8e2bbf14dfb 100644
--- a/src/server/game/Server/Packets/AchievementPackets.h
+++ b/src/server/game/Server/Packets/AchievementPackets.h
@@ -22,6 +22,7 @@
 #include "ObjectGuid.h"
 #include "Optional.h"
 #include "PacketUtilities.h"
+#include "WowTime.h"
 
 namespace WorldPackets
 {
@@ -30,7 +31,7 @@ namespace WorldPackets
         struct EarnedAchievement
         {
             uint32 Id = 0;
-            time_t Date = time_t(0);
+            WowTime Date;
             ObjectGuid Owner;
             uint32 VirtualRealmAddress = 0;
             uint32 NativeRealmAddress = 0;
@@ -43,7 +44,7 @@ namespace WorldPackets
             ObjectGuid Player;
             uint32 Unused_10_1_5 = 0;
             uint32 Flags = 0;
-            time_t Date = time_t(0);
+            WowTime Date;
             Duration<Seconds> TimeFromStart;
             Duration<Seconds> TimeFromCreate;
             Optional<uint64> RafAcceptanceID;
@@ -98,7 +99,7 @@ namespace WorldPackets
             ObjectGuid PlayerGUID;
             uint32 Unused_10_1_5 = 0;
             uint32 Flags = 0;
-            time_t CurrentTime = time_t(0);
+            WowTime CurrentTime;
             Duration<Seconds> ElapsedTime;
             Timestamp<> CreationTime;
             Optional<uint64> RafAcceptanceID;
@@ -146,7 +147,7 @@ namespace WorldPackets
             uint32 EarnerNativeRealm = 0;
             uint32 EarnerVirtualRealm = 0;
             uint32 AchievementID = 0;
-            time_t Time = time_t(0);
+            WowTime Time;
             bool Initial = false;
             ObjectGuid Sender;
         };
@@ -169,7 +170,7 @@ namespace WorldPackets
             int32 CriteriaID = 0;
             Timestamp<> DateCreated;
             Timestamp<> DateStarted;
-            time_t DateUpdated = 0;
+            WowTime DateUpdated;
             uint64 Quantity = 0;
             ObjectGuid PlayerGUID;
             int32 Unused_10_1_5 = 0;
@@ -216,7 +217,7 @@ namespace WorldPackets
 
             ObjectGuid GuildGUID;
             uint32 AchievementID = 0;
-            time_t TimeDeleted = time_t(0);
+            WowTime TimeDeleted;
         };
 
         class GuildAchievementEarned final : public ServerPacket
@@ -228,7 +229,7 @@ namespace WorldPackets
 
             uint32 AchievementID = 0;
             ObjectGuid GuildGUID;
-            time_t TimeEarned = time_t(0);
+            WowTime TimeEarned;
         };
 
         class AllGuildAchievements final : public ServerPacket
@@ -272,9 +273,9 @@ namespace WorldPackets
             int32 AchievementID = 0;
             std::vector<GuildAchievementMember> Member;
         };
+
+        ByteBuffer& operator<<(ByteBuffer& data, CriteriaProgress const& criteria);
     }
 }
 
-ByteBuffer& operator<<(ByteBuffer& data, WorldPackets::Achievement::CriteriaProgress const& criteria);
-
 #endif // game_AchievementPackets_h__
diff --git a/src/server/game/Server/Packets/CalendarPackets.cpp b/src/server/game/Server/Packets/CalendarPackets.cpp
index 27a67d416a3..cd0e1d3d7be 100644
--- a/src/server/game/Server/Packets/CalendarPackets.cpp
+++ b/src/server/game/Server/Packets/CalendarPackets.cpp
@@ -21,7 +21,7 @@ ByteBuffer& operator<<(ByteBuffer& data, WorldPackets::Calendar::CalendarSendCal
 {
     data << uint64(eventInfo.EventID);
     data << uint8(eventInfo.EventType);
-    data.AppendPackedTime(eventInfo.Date);
+    data << eventInfo.Date;
     data << uint32(eventInfo.Flags);
     data << int32(eventInfo.TextureID);
     data << uint64(eventInfo.EventClubID);
@@ -67,8 +67,7 @@ ByteBuffer& operator<<(ByteBuffer& data, WorldPackets::Calendar::CalendarEventIn
     data << uint8(inviteInfo.Status);
     data << uint8(inviteInfo.Moderator);
     data << uint8(inviteInfo.InviteType);
-
-    data.AppendPackedTime(inviteInfo.ResponseTime);
+    data << inviteInfo.ResponseTime;
 
     data.WriteBits(inviteInfo.Notes.size(), 8);
     data.FlushBits();
@@ -121,7 +120,7 @@ ByteBuffer& operator>>(ByteBuffer& buffer, WorldPackets::Calendar::CalendarAddEv
     buffer >> addEventInfo.ClubID;
     buffer >> addEventInfo.EventType;
     buffer >> addEventInfo.TextureID;
-    addEventInfo.Time = buffer.ReadPackedTime();
+    buffer >> addEventInfo.Time;
     buffer >> addEventInfo.Flags;
     addEventInfo.Invites.resize(buffer.read<uint32>());
 
@@ -150,7 +149,7 @@ ByteBuffer& operator>>(ByteBuffer& buffer, WorldPackets::Calendar::CalendarUpdat
     buffer >> updateEventInfo.ModeratorID;
     buffer >> updateEventInfo.EventType;
     buffer >> updateEventInfo.TextureID;
-    updateEventInfo.Time = buffer.ReadPackedTime();
+    buffer >> updateEventInfo.Time;
     buffer >> updateEventInfo.Flags;
 
     uint8 titleLen = buffer.ReadBits(8);
@@ -181,7 +180,7 @@ void WorldPackets::Calendar::CalendarCopyEvent::Read()
     _worldPacket >> EventID;
     _worldPacket >> ModeratorID;
     _worldPacket >> EventClubID;
-    Date = _worldPacket.ReadPackedTime();
+    _worldPacket >> Date;
 }
 
 void WorldPackets::Calendar::CalendarRSVP::Read()
@@ -252,7 +251,7 @@ WorldPacket const* WorldPackets::Calendar::CalendarInviteAdded::Write()
     _worldPacket << uint8(Level);
     _worldPacket << uint8(Status);
     _worldPacket << uint8(Type);
-    _worldPacket.AppendPackedTime(ResponseTime);
+    _worldPacket << ResponseTime;
 
     _worldPacket.WriteBit(ClearPending);
     _worldPacket.FlushBits();
@@ -262,7 +261,7 @@ WorldPacket const* WorldPackets::Calendar::CalendarInviteAdded::Write()
 
 WorldPacket const* WorldPackets::Calendar::CalendarSendCalendar::Write()
 {
-    _worldPacket.AppendPackedTime(ServerTime);
+    _worldPacket << ServerTime;
     _worldPacket << uint32(Invites.size());
     _worldPacket << uint32(Events.size());
     _worldPacket << uint32(RaidLockouts.size());
@@ -287,8 +286,8 @@ WorldPacket const* WorldPackets::Calendar::CalendarSendEvent::Write()
     _worldPacket << uint8(GetEventType);
     _worldPacket << int32(TextureID);
     _worldPacket << uint32(Flags);
-    _worldPacket.AppendPackedTime(Date);
-    _worldPacket << uint32(LockDate);
+    _worldPacket << Date;
+    _worldPacket << LockDate;
     _worldPacket << uint64(EventClubID);
     _worldPacket << uint32(Invites.size());
     _worldPacket.WriteBits(EventName.size(), 8);
@@ -307,7 +306,7 @@ WorldPacket const* WorldPackets::Calendar::CalendarSendEvent::Write()
 WorldPacket const* WorldPackets::Calendar::CalendarInviteAlert::Write()
 {
     _worldPacket << uint64(EventID);
-    _worldPacket.AppendPackedTime(Date);
+    _worldPacket << Date;
     _worldPacket << uint32(Flags);
     _worldPacket << uint8(EventType);
     _worldPacket << int32(TextureID);
@@ -331,10 +330,10 @@ WorldPacket const* WorldPackets::Calendar::CalendarInviteStatus::Write()
 {
     _worldPacket << InviteGuid;
     _worldPacket << uint64(EventID);
-    _worldPacket.AppendPackedTime(Date);
+    _worldPacket << Date;
     _worldPacket << uint32(Flags);
     _worldPacket << uint8(Status);
-    _worldPacket.AppendPackedTime(ResponseTime);
+    _worldPacket << ResponseTime;
 
     _worldPacket.WriteBit(ClearPending);
     _worldPacket.FlushBits();
@@ -369,7 +368,7 @@ WorldPacket const* WorldPackets::Calendar::CalendarModeratorStatus::Write()
 WorldPacket const* WorldPackets::Calendar::CalendarInviteRemovedAlert::Write()
 {
     _worldPacket << uint64(EventID);
-    _worldPacket.AppendPackedTime(Date);
+    _worldPacket << Date;
     _worldPacket << uint32(Flags);
     _worldPacket << uint8(Status);
 
@@ -381,9 +380,9 @@ WorldPacket const* WorldPackets::Calendar::CalendarEventUpdatedAlert::Write()
     _worldPacket << uint64(EventClubID);
     _worldPacket << uint64(EventID);
 
-    _worldPacket.AppendPackedTime(OriginalDate);
-    _worldPacket.AppendPackedTime(Date);
-    _worldPacket << uint32(LockDate);
+    _worldPacket << OriginalDate;
+    _worldPacket << Date;
+    _worldPacket << LockDate;
     _worldPacket << uint32(Flags);
     _worldPacket << uint32(TextureID);
     _worldPacket << uint8(EventType);
@@ -402,7 +401,7 @@ WorldPacket const* WorldPackets::Calendar::CalendarEventUpdatedAlert::Write()
 WorldPacket const* WorldPackets::Calendar::CalendarEventRemovedAlert::Write()
 {
     _worldPacket << uint64(EventID);
-    _worldPacket.AppendPackedTime(Date);
+    _worldPacket << Date;
 
     _worldPacket.WriteBit(ClearPending);
     _worldPacket.FlushBits();
@@ -450,7 +449,7 @@ WorldPacket const* WorldPackets::Calendar::CalendarRaidLockoutRemoved::Write()
 
 WorldPacket const* WorldPackets::Calendar::CalendarRaidLockoutUpdated::Write()
 {
-    _worldPacket.AppendPackedTime(ServerTime);
+    _worldPacket << ServerTime;
     _worldPacket << int32(MapID);
     _worldPacket << uint32(DifficultyID);
     _worldPacket << int32(OldTimeRemaining);
@@ -474,7 +473,7 @@ WorldPacket const* WorldPackets::Calendar::CalendarCommunityInvite::Write()
 WorldPacket const* WorldPackets::Calendar::CalendarInviteStatusAlert::Write()
 {
     _worldPacket << uint64(EventID);
-    _worldPacket.AppendPackedTime(Date);
+    _worldPacket << Date;
     _worldPacket << uint32(Flags);
     _worldPacket << uint8(Status);
 
diff --git a/src/server/game/Server/Packets/CalendarPackets.h b/src/server/game/Server/Packets/CalendarPackets.h
index 7ef1a4976f8..4ac9b9b8a3b 100644
--- a/src/server/game/Server/Packets/CalendarPackets.h
+++ b/src/server/game/Server/Packets/CalendarPackets.h
@@ -23,6 +23,7 @@
 #include "ObjectGuid.h"
 #include "Optional.h"
 #include "PacketUtilities.h"
+#include "WowTime.h"
 
 namespace WorldPackets
 {
@@ -76,7 +77,7 @@ namespace WorldPackets
             std::string Description;
             uint8 EventType = 0;
             int32 TextureID = 0;
-            time_t Time = time_t(0);
+            WowTime Time;
             uint32 Flags = 0;
             Array<CalendarAddEventInviteInfo, CALENDAR_MAX_INVITES> Invites;
         };
@@ -101,7 +102,7 @@ namespace WorldPackets
             std::string Description;
             uint8 EventType = 0;
             uint32 TextureID = 0;
-            time_t Time = time_t(0);
+            WowTime Time;
             uint32 Flags = 0;
         };
 
@@ -139,7 +140,7 @@ namespace WorldPackets
             uint64 ModeratorID = 0;
             uint64 EventID = 0;
             uint64 EventClubID = 0;
-            time_t Date = time_t(0);
+            WowTime Date;
         };
 
         class CalendarInviteAdded final : public ServerPacket
@@ -150,7 +151,7 @@ namespace WorldPackets
             WorldPacket const* Write() override;
 
             uint64 InviteID = 0;
-            time_t ResponseTime = time_t(0);
+            WowTime ResponseTime;
             uint8 Level = 100;
             ObjectGuid InviteGuid;
             uint64 EventID = 0;
@@ -183,7 +184,7 @@ namespace WorldPackets
             uint64 EventID = 0;
             std::string EventName;
             uint8 EventType = 0;
-            time_t Date = time_t(0);
+            WowTime Date;
             uint32 Flags = 0;
             int32 TextureID = 0;
             uint64 EventClubID = 0;
@@ -197,7 +198,7 @@ namespace WorldPackets
 
             WorldPacket const* Write() override;
 
-            time_t ServerTime = time_t(0);
+            WowTime ServerTime;
             std::vector<CalendarSendCalendarInviteInfo> Invites;
             std::vector<CalendarSendCalendarRaidLockoutInfo> RaidLockouts;
             std::vector<CalendarSendCalendarEventInfo> Events;
@@ -207,7 +208,7 @@ namespace WorldPackets
         {
             ObjectGuid Guid;
             uint64 InviteID = 0;
-            time_t ResponseTime = time_t(0);
+            WowTime ResponseTime;
             uint8 Level = 1;
             uint8 Status = 0;
             uint8 Moderator = 0;
@@ -225,8 +226,8 @@ namespace WorldPackets
             ObjectGuid OwnerGuid;
             uint64 EventClubID = 0;
             uint64 EventID = 0;
-            time_t Date = time_t(0);
-            time_t LockDate = time_t(0);
+            WowTime Date;
+            WowTime LockDate;
             uint32 Flags = 0;
             int32 TextureID = 0;
             uint8 GetEventType = 0;
@@ -249,7 +250,7 @@ namespace WorldPackets
             uint64 InviteID = 0;
             uint64 EventID = 0;
             uint32 Flags = 0;
-            time_t Date = time_t(0);
+            WowTime Date;
             int32 TextureID = 0;
             uint8 Status = 0;
             uint8 EventType = 0;
@@ -295,8 +296,8 @@ namespace WorldPackets
             uint64 EventID = 0;
             uint8 Status = 0;
             bool ClearPending = false;
-            time_t ResponseTime = time_t(0);
-            time_t Date = time_t(0);
+            WowTime ResponseTime;
+            WowTime Date;
             ObjectGuid InviteGuid;
         };
 
@@ -334,7 +335,7 @@ namespace WorldPackets
             WorldPacket const* Write() override;
 
             uint64 EventID = 0;
-            time_t Date = time_t(0);
+            WowTime Date;
             uint32 Flags = 0;
             uint8 Status = 0;
         };
@@ -356,10 +357,10 @@ namespace WorldPackets
 
             uint64 EventClubID = 0;
             uint64 EventID = 0;
-            time_t Date = time_t(0);
+            WowTime Date;
             uint32 Flags = 0;
-            time_t LockDate = time_t(0);
-            time_t OriginalDate = time_t(0);
+            WowTime LockDate;
+            WowTime OriginalDate;
             int32 TextureID = 0;
             uint8 EventType = 0;
             bool ClearPending = false;
@@ -375,7 +376,7 @@ namespace WorldPackets
             WorldPacket const* Write() override;
 
             uint64 EventID = 0;
-            time_t Date = time_t(0);
+            WowTime Date;
             bool ClearPending = false;
         };
 
@@ -509,7 +510,7 @@ namespace WorldPackets
 
             WorldPacket const* Write() override;
 
-            time_t ServerTime = 0;
+            WowTime ServerTime;
             int32 MapID = 0;
             uint32 DifficultyID = 0;
             int32 NewTimeRemaining = 0;
@@ -543,7 +544,7 @@ namespace WorldPackets
 
             uint64 EventID = 0;
             uint32 Flags = 0;
-            time_t Date = time_t(0);
+            WowTime Date;
             uint8 Status = 0;
         };
 
diff --git a/src/server/game/Server/Packets/GuildPackets.cpp b/src/server/game/Server/Packets/GuildPackets.cpp
index aa59ebfc986..fe80b31595d 100644
--- a/src/server/game/Server/Packets/GuildPackets.cpp
+++ b/src/server/game/Server/Packets/GuildPackets.cpp
@@ -64,7 +64,7 @@ WorldPacket const* WorldPackets::Guild::QueryGuildInfoResponse::Write()
 WorldPacket const* WorldPackets::Guild::GuildRoster::Write()
 {
     _worldPacket << int32(NumAccounts);
-    _worldPacket.AppendPackedTime(CreateDate);
+    _worldPacket << CreateDate;
     _worldPacket << int32(GuildFlags);
     _worldPacket << uint32(MemberData.size());
     _worldPacket.WriteBits(WelcomeText.length(), 11);
@@ -871,7 +871,7 @@ void WorldPackets::Guild::GuildQueryNews::Read()
 ByteBuffer& operator<<(ByteBuffer& data, WorldPackets::Guild::GuildNewsEvent const& newsEvent)
 {
     data << int32(newsEvent.Id);
-    data.AppendPackedTime(newsEvent.CompletedDate);
+    data << newsEvent.CompletedDate;
     data << int32(newsEvent.Type);
     data << int32(newsEvent.Flags);
 
diff --git a/src/server/game/Server/Packets/GuildPackets.h b/src/server/game/Server/Packets/GuildPackets.h
index bd80498061e..31f9c6ba62d 100644
--- a/src/server/game/Server/Packets/GuildPackets.h
+++ b/src/server/game/Server/Packets/GuildPackets.h
@@ -24,6 +24,7 @@
 #include "MythicPlusPacketsCommon.h"
 #include "ObjectGuid.h"
 #include "PacketUtilities.h"
+#include "WowTime.h"
 
 namespace WorldPackets
 {
@@ -130,7 +131,7 @@ namespace WorldPackets
             std::vector<GuildRosterMemberData> MemberData;
             std::string WelcomeText;
             std::string InfoText;
-            uint32 CreateDate = 0;
+            WowTime CreateDate;
             int32 NumAccounts = 0;
             int32 GuildFlags = 0;
         };
@@ -1073,7 +1074,7 @@ namespace WorldPackets
         struct GuildNewsEvent
         {
             int32 Id = 0;
-            uint32 CompletedDate = 0;
+            WowTime CompletedDate;
             int32 Type = 0;
             int32 Flags = 0;
             std::array<int32, 2> Data = { };
diff --git a/src/server/game/Server/Packets/MiscPackets.cpp b/src/server/game/Server/Packets/MiscPackets.cpp
index 9c6687075af..21395173965 100644
--- a/src/server/game/Server/Packets/MiscPackets.cpp
+++ b/src/server/game/Server/Packets/MiscPackets.cpp
@@ -36,8 +36,8 @@ WorldPacket const* WorldPackets::Misc::InvalidatePlayer::Write()
 
 WorldPacket const* WorldPackets::Misc::LoginSetTimeSpeed::Write()
 {
-    _worldPacket.AppendPackedTime(ServerTime);
-    _worldPacket.AppendPackedTime(GameTime);
+    _worldPacket << ServerTime;
+    _worldPacket << GameTime;
     _worldPacket << float(NewSpeed);
     _worldPacket << uint32(ServerTimeHolidayOffset);
     _worldPacket << uint32(GameTimeHolidayOffset);
diff --git a/src/server/game/Server/Packets/MiscPackets.h b/src/server/game/Server/Packets/MiscPackets.h
index ef5de8330d6..b1469847788 100644
--- a/src/server/game/Server/Packets/MiscPackets.h
+++ b/src/server/game/Server/Packets/MiscPackets.h
@@ -28,6 +28,7 @@
 #include "Player.h"
 #include "Position.h"
 #include "SharedDefines.h"
+#include "WowTime.h"
 #include <array>
 #include <map>
 
@@ -81,8 +82,8 @@ namespace WorldPackets
 
             float NewSpeed = 0.0f;
             int32 ServerTimeHolidayOffset = 0;
-            uint32 GameTime = 0;
-            uint32 ServerTime = 0;
+            WowTime GameTime;
+            WowTime ServerTime;
             int32 GameTimeHolidayOffset = 0;
         };
 
diff --git a/src/server/game/Server/Packets/SystemPackets.h b/src/server/game/Server/Packets/SystemPackets.h
index 5c173e7d3ac..afb0600db98 100644
--- a/src/server/game/Server/Packets/SystemPackets.h
+++ b/src/server/game/Server/Packets/SystemPackets.h
@@ -234,9 +234,9 @@ namespace WorldPackets
 
             WorldPacket const* Write() override;
 
-            std::string ServerTimeTZ;
-            std::string GameTimeTZ;
-            std::string ServerRegionalTZ;
+            std::string_view ServerTimeTZ;
+            std::string_view GameTimeTZ;
+            std::string_view ServerRegionalTZ;
         };
     }
 }
diff --git a/src/server/game/Server/WorldSession.cpp b/src/server/game/Server/WorldSession.cpp
index c4c46c044d9..2f4a333529f 100644
--- a/src/server/game/Server/WorldSession.cpp
+++ b/src/server/game/Server/WorldSession.cpp
@@ -106,7 +106,7 @@ bool WorldSessionFilter::Process(WorldPacket* packet)
 
 /// WorldSession constructor
 WorldSession::WorldSession(uint32 id, std::string&& name, uint32 battlenetAccountId, std::shared_ptr<WorldSocket> sock, AccountTypes sec, uint8 expansion, time_t mute_time,
-    std::string os, LocaleConstant locale, uint32 recruiter, bool isARecruiter):
+    std::string os, Minutes timezoneOffset, LocaleConstant locale, uint32 recruiter, bool isARecruiter):
     m_muteTime(mute_time),
     m_timeOutTime(0),
     AntiDOS(this),
@@ -118,7 +118,7 @@ WorldSession::WorldSession(uint32 id, std::string&& name, uint32 battlenetAccoun
     _battlenetAccountId(battlenetAccountId),
     m_accountExpansion(expansion),
     m_expansion(std::min<uint8>(expansion, sWorld->getIntConfig(CONFIG_EXPANSION))),
-    _os(os),
+    _os(std::move(os)),
     _battlenetRequestToken(0),
     _logoutTime(0),
     m_inQueue(false),
@@ -127,6 +127,7 @@ WorldSession::WorldSession(uint32 id, std::string&& name, uint32 battlenetAccoun
     m_playerSave(false),
     m_sessionDbcLocale(sWorld->GetAvailableDbcLocale(locale)),
     m_sessionDbLocaleIndex(locale),
+    _timezoneOffset(timezoneOffset),
     m_latency(0),
     _tutorialsChanged(TUTORIALS_FLAG_NONE),
     _filterAddonMessages(false),
@@ -153,7 +154,7 @@ WorldSession::WorldSession(uint32 id, std::string&& name, uint32 battlenetAccoun
         LoginDatabase.PExecute("UPDATE account SET online = 1 WHERE id = {};", GetAccountId());     // One-time query
     }
 
-    m_Socket[CONNECTION_TYPE_REALM] = sock;
+    m_Socket[CONNECTION_TYPE_REALM] = std::move(sock);
     _instanceConnectKey.Raw = UI64LIT(0);
 }
 
diff --git a/src/server/game/Server/WorldSession.h b/src/server/game/Server/WorldSession.h
index 2971a6f59ef..296eda86e61 100644
--- a/src/server/game/Server/WorldSession.h
+++ b/src/server/game/Server/WorldSession.h
@@ -948,7 +948,7 @@ class TC_GAME_API WorldSession
 {
     public:
         WorldSession(uint32 id, std::string&& name, uint32 battlenetAccountId, std::shared_ptr<WorldSocket> sock, AccountTypes sec, uint8 expansion, time_t mute_time,
-            std::string os, LocaleConstant locale, uint32 recruiter, bool isARecruiter);
+            std::string os, Minutes timezoneOffset, LocaleConstant locale, uint32 recruiter, bool isARecruiter);
         ~WorldSession();
 
         bool PlayerLoading() const { return !m_playerLoading.IsEmpty(); }
@@ -1131,6 +1131,9 @@ class TC_GAME_API WorldSession
         // Locales
         LocaleConstant GetSessionDbcLocale() const { return m_sessionDbcLocale; }
         LocaleConstant GetSessionDbLocaleIndex() const { return m_sessionDbLocaleIndex; }
+
+        Minutes GetTimezoneOffset() const { return _timezoneOffset; }
+
         char const* GetTrinityString(uint32 entry) const;
 
         uint32 GetLatency() const { return m_latency; }
@@ -1916,6 +1919,7 @@ class TC_GAME_API WorldSession
         bool m_playerSave;
         LocaleConstant m_sessionDbcLocale;
         LocaleConstant m_sessionDbLocaleIndex;
+        Minutes _timezoneOffset;
         std::atomic<uint32> m_latency;
         AccountData _accountData[NUM_ACCOUNT_DATA_TYPES];
         uint32 _tutorials[MAX_ACCOUNT_TUTORIAL_VALUES];
diff --git a/src/server/game/Server/WorldSocket.cpp b/src/server/game/Server/WorldSocket.cpp
index c92b8d03c8f..0161974879a 100644
--- a/src/server/game/Server/WorldSocket.cpp
+++ b/src/server/game/Server/WorldSocket.cpp
@@ -626,6 +626,7 @@ struct AccountInfo
         int64 MuteTime;
         uint32 Recruiter;
         std::string OS;
+        Minutes TimezoneOffset;
         bool IsRectuiter;
         AccountTypes Security;
         bool IsBanned;
@@ -633,11 +634,11 @@ struct AccountInfo
 
     bool IsBanned() const { return BattleNet.IsBanned || Game.IsBanned; }
 
-    explicit AccountInfo(Field* fields)
+    explicit AccountInfo(Field const* fields)
     {
-        //           0              1           2          3                4            5           6          7            8     9     10                11
-        // SELECT a.id, a.session_key, ba.last_ip, ba.locked, ba.lock_country, a.expansion, a.mutetime, ba.locale, a.recruiter, a.os, ba.id, aa.SecurityLevel,
-        //                                                              12                                                            13    14
+        //           0              1           2          3                4            5           6          7            8     9                 10     11                12
+        // SELECT a.id, a.session_key, ba.last_ip, ba.locked, ba.lock_country, a.expansion, a.mutetime, ba.locale, a.recruiter, a.os, a.timezone_offset, ba.id, aa.SecurityLevel,
+        //                                                              13                                                            14    15
         // bab.unbandate > UNIX_TIMESTAMP() OR bab.unbandate = bab.bandate, ab.unbandate > UNIX_TIMESTAMP() OR ab.unbandate = ab.bandate, r.id
         // FROM account a LEFT JOIN battlenet_accounts ba ON a.battlenet_account = ba.id LEFT JOIN account_access aa ON a.id = aa.AccountID AND aa.RealmID IN (-1, ?)
         // LEFT JOIN battlenet_account_bans bab ON ba.id = bab.id LEFT JOIN account_banned ab ON a.id = ab.id LEFT JOIN account r ON a.id = r.recruiter
@@ -652,11 +653,12 @@ struct AccountInfo
         BattleNet.Locale = LocaleConstant(fields[7].GetUInt8());
         Game.Recruiter = fields[8].GetUInt32();
         Game.OS = fields[9].GetString();
-        BattleNet.Id = fields[10].GetUInt32();
-        Game.Security = AccountTypes(fields[11].GetUInt8());
-        BattleNet.IsBanned = fields[12].GetUInt32() != 0;
-        Game.IsBanned = fields[13].GetUInt32() != 0;
-        Game.IsRectuiter = fields[14].GetUInt32() != 0;
+        Game.TimezoneOffset = Minutes(fields[10].GetInt16());
+        BattleNet.Id = fields[11].GetUInt32();
+        Game.Security = AccountTypes(fields[12].GetUInt8());
+        BattleNet.IsBanned = fields[13].GetUInt32() != 0;
+        Game.IsBanned = fields[14].GetUInt32() != 0;
+        Game.IsRectuiter = fields[15].GetUInt32() != 0;
 
         if (BattleNet.Locale >= TOTAL_LOCALES)
             BattleNet.Locale = LOCALE_enUS;
@@ -670,7 +672,10 @@ void WorldSocket::HandleAuthSession(std::shared_ptr<WorldPackets::Auth::AuthSess
     stmt->setInt32(0, int32(realm.Id.Realm));
     stmt->setString(1, authSession->RealmJoinTicket);
 
-    _queryProcessor.AddCallback(LoginDatabase.AsyncQuery(stmt).WithPreparedCallback(std::bind(&WorldSocket::HandleAuthSessionCallback, this, authSession, std::placeholders::_1)));
+    _queryProcessor.AddCallback(LoginDatabase.AsyncQuery(stmt).WithPreparedCallback([this, authSession = std::move(authSession)](PreparedQueryResult result) mutable
+    {
+        HandleAuthSessionCallback(std::move(authSession), std::move(result));
+    }));
 }
 
 void WorldSocket::HandleAuthSessionCallback(std::shared_ptr<WorldPackets::Auth::AuthSession> authSession, PreparedQueryResult result)
@@ -868,7 +873,7 @@ void WorldSocket::HandleAuthSessionCallback(std::shared_ptr<WorldPackets::Auth::
 
     _authed = true;
     _worldSession = new WorldSession(account.Game.Id, std::move(authSession->RealmJoinTicket), account.BattleNet.Id, shared_from_this(), account.Game.Security,
-        account.Game.Expansion, mutetime, account.Game.OS, account.BattleNet.Locale, account.Game.Recruiter, account.Game.IsRectuiter);
+        account.Game.Expansion, mutetime, account.Game.OS, account.Game.TimezoneOffset, account.BattleNet.Locale, account.Game.Recruiter, account.Game.IsRectuiter);
 
     // Initialize Warden system only if it is enabled by config
     if (wardenActive)
diff --git a/src/server/game/Services/WorldserverService.cpp b/src/server/game/Services/WorldserverService.cpp
index 61a13011f4b..213ffbbad8f 100644
--- a/src/server/game/Services/WorldserverService.cpp
+++ b/src/server/game/Services/WorldserverService.cpp
@@ -126,7 +126,7 @@ uint32 Battlenet::GameUtilitiesService::HandleRealmJoinRequest(std::unordered_ma
 {
     if (Variant const* realmAddress = GetParam(params, "Param_RealmAddress"))
         return sRealmList->JoinRealm(uint32(realmAddress->uint_value()), realm.Build, Trinity::Net::make_address(_session->GetRemoteAddress()), _session->GetRealmListSecret(),
-            _session->GetSessionDbcLocale(), _session->GetOS(), _session->GetAccountName(), response);
+            _session->GetSessionDbcLocale(), _session->GetOS(), _session->GetTimezoneOffset(), _session->GetAccountName(), response);
 
     return ERROR_WOW_SERVICES_INVALID_JOIN_TICKET;
 }
diff --git a/src/server/game/Time/GameTime.cpp b/src/server/game/Time/GameTime.cpp
index 399be3196b3..3175c0e5571 100644
--- a/src/server/game/Time/GameTime.cpp
+++ b/src/server/game/Time/GameTime.cpp
@@ -17,7 +17,9 @@
 
 #include "GameTime.h"
 #include "Timer.h"
+#include "Timezone.h"
 #include "Util.h"
+#include "WowTime.h"
 
 namespace GameTime
 {
@@ -31,6 +33,9 @@ namespace GameTime
 
     tm DateTime;
 
+    WowTime UtcWow;
+    WowTime Wow;
+
     time_t GetStartTime()
     {
         return StartTime;
@@ -84,6 +89,16 @@ namespace GameTime
         return &DateTime;
     }
 
+    WowTime const* GetUtcWowTime()
+    {
+        return &UtcWow;
+    }
+
+    WowTime const* GetWowTime()
+    {
+        return &Wow;
+    }
+
     void UpdateGameTimers()
     {
         GameTime = time(nullptr);
@@ -91,5 +106,7 @@ namespace GameTime
         GameTimeSystemPoint = std::chrono::system_clock::now();
         GameTimeSteadyPoint = std::chrono::steady_clock::now();
         localtime_r(&GameTime, &DateTime);
+        UtcWow.SetUtcTimeFromUnixTime(GameTime);
+        Wow = UtcWow + Trinity::Timezone::GetSystemZoneOffsetAt(GameTimeSystemPoint);
     }
 }
diff --git a/src/server/game/Time/GameTime.h b/src/server/game/Time/GameTime.h
index 4229872e016..7b18b030d2c 100644
--- a/src/server/game/Time/GameTime.h
+++ b/src/server/game/Time/GameTime.h
@@ -21,6 +21,8 @@
 #include "Define.h"
 #include "Duration.h"
 
+class WowTime;
+
 namespace GameTime
 {
     // Server start time
@@ -47,6 +49,10 @@ namespace GameTime
 
     TC_GAME_API tm const* GetDateAndTime();
 
+    TC_GAME_API WowTime const* GetUtcWowTime();
+
+    TC_GAME_API WowTime const* GetWowTime();
+
     void UpdateGameTimers();
 }
 
diff --git a/src/server/game/Time/WowTime.cpp b/src/server/game/Time/WowTime.cpp
new file mode 100644
index 00000000000..b88f0c56a8e
--- /dev/null
+++ b/src/server/game/Time/WowTime.cpp
@@ -0,0 +1,219 @@
+/*
+ * This file is part of the TrinityCore Project. See AUTHORS file for Copyright information
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the
+ * Free Software Foundation; either version 2 of the License, or (at your
+ * option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "WowTime.h"
+#include "ByteBuffer.h"
+#include "Errors.h"
+#include "Util.h"
+
+uint32 WowTime::GetPackedTime() const
+{
+    return ((_year % 100) & 0x1F) << 24
+        | (_month & 0xF) << 20
+        | (_monthDay & 0x3F) << 14
+        | (_weekDay & 0x7) << 11
+        | (_hour & 0x1F) << 6
+        | (_minute & 0x3F)
+        | (_flags & 0x3) << 29;
+}
+
+void WowTime::SetPackedTime(uint32 packedTime)
+{
+    _year = (packedTime >> 24) & 0x1F;
+    if (_year == 31)
+        _year = -1;
+
+    _month = (packedTime >> 20) & 0xF;
+    if (_month == 15)
+        _month = -1;
+
+    _monthDay = (packedTime >> 14) & 0x3F;
+    if (_monthDay == 63)
+        _monthDay = -1;
+
+    _weekDay = (packedTime >> 11) & 0x7;
+    if (_weekDay == 7)
+        _weekDay = -1;
+
+    _hour = (packedTime >> 6) & 0x1F;
+    if (_hour == 31)
+        _hour = -1;
+
+    _minute = packedTime & 0x3F;
+    if (_minute == 63)
+        _minute = -1;
+
+    _flags = (packedTime >> 29) & 0x3;
+    if (_flags == 3)
+        _flags = -1;
+}
+
+std::time_t WowTime::GetUnixTimeFromUtcTime() const
+{
+    if (_year < 0 || _month < 0 || _monthDay < 0)
+        return 0;
+
+    std::tm buf{};
+    buf.tm_year = _year + 100;
+    buf.tm_mon = _month;
+    buf.tm_mday = _monthDay + 1;
+    if (_hour >= 0)
+    {
+        buf.tm_hour = _hour;
+        if (_minute >= 0)
+            buf.tm_min = _minute;
+    }
+    buf.tm_isdst = -1;
+    buf.tm_wday = _weekDay;
+
+    return timegm(&buf);
+}
+
+void WowTime::SetUtcTimeFromUnixTime(std::time_t unixTime)
+{
+    std::tm buf;
+    if (!::gmtime_r(&unixTime, &buf))
+        return;
+
+    _year = (buf.tm_year - 100) % 100;
+    _month = buf.tm_mon;
+    _monthDay = buf.tm_mday - 1;
+    _weekDay = buf.tm_wday;
+    _hour = buf.tm_hour;
+    _minute = buf.tm_min;
+}
+
+void WowTime::SetYear(int32 year)
+{
+    ASSERT(year == -1 || (year >= 0 && year < 32));
+    _year = year;
+}
+
+void WowTime::SetMonth(int8 month)
+{
+    ASSERT(month == -1 || (month >= 0 && month < 12));
+    _month = month;
+}
+
+void WowTime::SetMonthDay(int8 monthDay)
+{
+    ASSERT(monthDay == -1 || (monthDay >= 0 && monthDay < 32));
+    _monthDay = monthDay;
+}
+
+void WowTime::SetWeekDay(int8 weekDay)
+{
+    ASSERT(weekDay == -1 || (weekDay >= 0 && weekDay < 7));
+    _weekDay = weekDay;
+}
+
+void WowTime::SetHour(int8 hour)
+{
+    ASSERT(hour == -1 || (hour >= 0 && hour < 24));
+    _hour = hour;
+}
+
+void WowTime::SetMinute(int8 minute)
+{
+    ASSERT(minute == -1 || (minute >= 0 && minute < 60));
+    _minute = minute;
+}
+
+void WowTime::SetFlags(int8 flags)
+{
+    ASSERT(flags == -1 || (flags >= 0 && flags < 3));
+    _flags = flags;
+}
+
+std::strong_ordering operator<=>(WowTime const& left, WowTime const& right)
+{
+    auto compareFieldIfSet = [&]<typename T>(T WowTime::*field) -> std::strong_ordering
+    {
+        if (left.*field < 0 || right.*field < 0)
+            return std::strong_ordering::equal;
+
+        return left.*field <=> right.*field;
+    };
+
+    if (std::strong_ordering cmp = compareFieldIfSet(&WowTime::_year); advstd::is_neq(cmp))
+        return cmp;
+
+    if (std::strong_ordering cmp = compareFieldIfSet(&WowTime::_month); advstd::is_neq(cmp))
+        return cmp;
+
+    if (std::strong_ordering cmp = compareFieldIfSet(&WowTime::_monthDay); advstd::is_neq(cmp))
+        return cmp;
+
+    if (std::strong_ordering cmp = compareFieldIfSet(&WowTime::_weekDay); advstd::is_neq(cmp))
+        return cmp;
+
+    if (std::strong_ordering cmp = compareFieldIfSet(&WowTime::_year); advstd::is_neq(cmp))
+        return cmp;
+
+    if (std::strong_ordering cmp = compareFieldIfSet(&WowTime::_hour); advstd::is_neq(cmp))
+        return cmp;
+
+    return std::strong_ordering::equal;
+}
+
+bool WowTime::IsInRange(WowTime const& from, WowTime const& to) const
+{
+    if (from > to)
+        return *this >= from || *this < to;
+
+    return *this >= from && *this < to;
+}
+
+WowTime& WowTime::operator+=(Seconds seconds)
+{
+    time_t unixTime = GetUnixTimeFromUtcTime();
+    unixTime += seconds.count();
+    SetUtcTimeFromUnixTime(unixTime);
+    return *this;
+}
+
+WowTime WowTime::operator+(Seconds seconds) const
+{
+    return WowTime(*this) += seconds;
+}
+
+WowTime& WowTime::operator-=(Seconds seconds)
+{
+    time_t unixTime = GetUnixTimeFromUtcTime();
+    unixTime -= seconds.count();
+    SetUtcTimeFromUnixTime(unixTime);
+    return *this;
+}
+
+WowTime WowTime::operator-(Seconds seconds) const
+{
+    return WowTime(*this) -= seconds;
+}
+
+ByteBuffer& operator<<(ByteBuffer& data, WowTime const& wowTime)
+{
+    data << uint32(wowTime.GetPackedTime());
+    return data;
+}
+
+ByteBuffer& operator>>(ByteBuffer& data, WowTime& wowTime)
+{
+    uint32 packedTime = 0;
+    data >> packedTime;
+    wowTime.SetPackedTime(packedTime);
+    return data;
+}
diff --git a/src/server/game/Time/WowTime.h b/src/server/game/Time/WowTime.h
new file mode 100644
index 00000000000..a273d210d6a
--- /dev/null
+++ b/src/server/game/Time/WowTime.h
@@ -0,0 +1,90 @@
+/*
+ * This file is part of the TrinityCore Project. See AUTHORS file for Copyright information
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the
+ * Free Software Foundation; either version 2 of the License, or (at your
+ * option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef TRINITYCORE_WOWTIME_H
+#define TRINITYCORE_WOWTIME_H
+
+#include "Define.h"
+#include "Duration.h"
+#include "advstd.h"
+#include <compare>
+#include <ctime>
+
+class ByteBuffer;
+
+class WowTime
+{
+public:
+    uint32 GetPackedTime() const;
+    void SetPackedTime(uint32 packedTime);
+
+    std::time_t GetUnixTimeFromUtcTime() const;
+    void SetUtcTimeFromUnixTime(std::time_t unixTime);
+
+    int32 GetYear() const { return _year; }
+    void SetYear(int32 year);
+
+    int8 GetMonth() const { return _month; }
+    void SetMonth(int8 month);
+
+    int8 GetMonthDay() const { return _monthDay; }
+    void SetMonthDay(int8 monthDay);
+
+    int8 GetWeekDay() const { return _weekDay; }
+    void SetWeekDay(int8 weekDay);
+
+    int8 GetHour() const { return _hour; }
+    void SetHour(int8 hour);
+
+    int8 GetMinute() const { return _minute; }
+    void SetMinute(int8 minute);
+
+    int8 GetFlags() const { return _flags; }
+    void SetFlags(int8 flags);
+
+    int8 GetHolidayOffset() const { return _holidayOffset; }
+    void SetHolidayOffset(int8 holidayOffset) { _holidayOffset = holidayOffset; }
+
+    friend TC_GAME_API std::strong_ordering operator<=>(WowTime const& left, WowTime const& right);
+    friend TC_GAME_API bool operator==(WowTime const& left, WowTime const& right)
+    {
+        return advstd::is_eq(left <=> right);
+    }
+
+    bool IsInRange(WowTime const& from, WowTime const& to) const;
+
+    WowTime& operator+=(Seconds seconds);
+    WowTime operator+(Seconds seconds) const;
+
+    WowTime& operator-=(Seconds seconds);
+    WowTime operator-(Seconds seconds) const;
+
+    friend TC_GAME_API ByteBuffer& operator<<(ByteBuffer& data, WowTime const& wowTime);
+    friend TC_GAME_API ByteBuffer& operator>>(ByteBuffer& data, WowTime& wowTime);
+
+private:
+    int32 _year = -1;
+    int8 _month = -1;
+    int8 _monthDay = -1;
+    int8 _weekDay = -1;
+    int8 _hour = -1;
+    int8 _minute = -1;
+    int8 _flags = -1;
+    int8 _holidayOffset = 0;
+};
+
+#endif // TRINITYCORE_WOWTIME_H
diff --git a/src/server/shared/Packets/ByteBuffer.cpp b/src/server/shared/Packets/ByteBuffer.cpp
index 1775192227a..104ba96d9d0 100644
--- a/src/server/shared/Packets/ByteBuffer.cpp
+++ b/src/server/shared/Packets/ByteBuffer.cpp
@@ -23,7 +23,6 @@
 #include <utf8.h>
 #include <sstream>
 #include <cmath>
-#include <ctime>
 
 ByteBuffer::ByteBuffer(MessageBuffer&& buffer) : _rpos(0), _wpos(0), _bitpos(InitialBitPos), _curbitval(0), _storage(buffer.Move())
 {
@@ -92,21 +91,6 @@ std::string ByteBuffer::ReadString(uint32 length, bool requireValidUtf8 /*= true
     return value;
 }
 
-uint32 ByteBuffer::ReadPackedTime()
-{
-    uint32 packedDate = read<uint32>();
-    tm lt = tm();
-
-    lt.tm_min = packedDate & 0x3F;
-    lt.tm_hour = (packedDate >> 6) & 0x1F;
-    //lt.tm_wday = (packedDate >> 11) & 7;
-    lt.tm_mday = ((packedDate >> 14) & 0x3F) + 1;
-    lt.tm_mon = (packedDate >> 20) & 0xF;
-    lt.tm_year = ((packedDate >> 24) & 0x1F) + 100;
-
-    return uint32(mktime(&lt));
-}
-
 void ByteBuffer::append(uint8 const* src, size_t cnt)
 {
     ASSERT(src, "Attempted to put a NULL-pointer in ByteBuffer (pos: " SZFMTD " size: " SZFMTD ")", _wpos, size());
@@ -134,13 +118,6 @@ void ByteBuffer::append(uint8 const* src, size_t cnt)
     _wpos = newSize;
 }
 
-void ByteBuffer::AppendPackedTime(time_t time)
-{
-    tm lt;
-    localtime_r(&time, &lt);
-    append<uint32>((lt.tm_year - 100) << 24 | lt.tm_mon << 20 | (lt.tm_mday - 1) << 14 | lt.tm_wday << 11 | lt.tm_hour << 6 | lt.tm_min);
-}
-
 void ByteBuffer::put(size_t pos, uint8 const* src, size_t cnt)
 {
     ASSERT(pos + cnt <= size(), "Attempted to put value with size: " SZFMTD " in ByteBuffer (pos: " SZFMTD " size: " SZFMTD ")", cnt, pos, size());
diff --git a/src/server/shared/Packets/ByteBuffer.h b/src/server/shared/Packets/ByteBuffer.h
index 76b521b9358..de0adf54341 100644
--- a/src/server/shared/Packets/ByteBuffer.h
+++ b/src/server/shared/Packets/ByteBuffer.h
@@ -519,8 +519,6 @@ class TC_SHARED_API ByteBuffer
 
         std::string ReadString(uint32 length, bool requireValidUtf8 = true);
 
-        uint32 ReadPackedTime();
-
         uint8* contents()
         {
             if (_storage.empty())
@@ -624,8 +622,6 @@ class TC_SHARED_API ByteBuffer
             return resultSize;
         }
 
-        void AppendPackedTime(time_t time);
-
         void put(size_t pos, uint8 const* src, size_t cnt);
 
         void print_storage() const;
diff --git a/src/server/shared/Realm/RealmList.cpp b/src/server/shared/Realm/RealmList.cpp
index 3d72418c10b..779bb6fca09 100644
--- a/src/server/shared/Realm/RealmList.cpp
+++ b/src/server/shared/Realm/RealmList.cpp
@@ -369,7 +369,7 @@ std::vector<uint8> RealmList::GetRealmList(uint32 build, std::string const& subR
 }
 
 uint32 RealmList::JoinRealm(uint32 realmAddress, uint32 build, boost::asio::ip::address const& clientAddress, std::array<uint8, 32> const& clientSecret,
-    LocaleConstant locale, std::string const& os, std::string accountName, bgs::protocol::game_utilities::v1::ClientResponse* response) const
+    LocaleConstant locale, std::string const& os, Minutes timezoneOffset, std::string const& accountName, bgs::protocol::game_utilities::v1::ClientResponse* response) const
 {
     std::shared_lock<std::shared_mutex> lock(_realmsMutex);
     if (Realm const* realm = GetRealm(Battlenet::RealmHandle(realmAddress)))
@@ -400,15 +400,17 @@ uint32 RealmList::JoinRealm(uint32 realmAddress, uint32 build, boost::asio::ip::
         std::array<uint8, 32> serverSecret = Trinity::Crypto::GetRandomBytes<32>();
 
         std::array<uint8, 64> keyData;
-        memcpy(&keyData[0], clientSecret.data(), 32);
-        memcpy(&keyData[32], serverSecret.data(), 32);
+        auto keyDestItr = keyData.begin();
+        keyDestItr = std::copy(clientSecret.begin(), clientSecret.end(), keyDestItr);
+        keyDestItr = std::copy(serverSecret.begin(), serverSecret.end(), keyDestItr);
 
         LoginDatabasePreparedStatement* stmt = LoginDatabase.GetPreparedStatement(LOGIN_UPD_BNET_GAME_ACCOUNT_LOGIN_INFO);
         stmt->setBinary(0, keyData);
         stmt->setString(1, clientAddress.to_string());
         stmt->setUInt8(2, locale);
         stmt->setString(3, os);
-        stmt->setString(4, accountName);
+        stmt->setInt16(4, timezoneOffset.count());
+        stmt->setString(5, accountName);
         LoginDatabase.DirectExecute(stmt);
 
         bgs::protocol::Attribute* attribute = response->add_attribute();
diff --git a/src/server/shared/Realm/RealmList.h b/src/server/shared/Realm/RealmList.h
index 973dd913d7a..a1262d7e913 100644
--- a/src/server/shared/Realm/RealmList.h
+++ b/src/server/shared/Realm/RealmList.h
@@ -19,6 +19,7 @@
 #define _REALMLIST_H
 
 #include "Define.h"
+#include "Duration.h"
 #include "Realm.h"
 #include <array>
 #include <map>
@@ -91,7 +92,8 @@ public:
     std::vector<uint8> GetRealmEntryJSON(Battlenet::RealmHandle const& id, uint32 build) const;
     std::vector<uint8> GetRealmList(uint32 build, std::string const& subRegion) const;
     uint32 JoinRealm(uint32 realmAddress, uint32 build, boost::asio::ip::address const& clientAddress, std::array<uint8, 32> const& clientSecret,
-        LocaleConstant locale, std::string const& os, std::string accountName, bgs::protocol::game_utilities::v1::ClientResponse* response) const;
+        LocaleConstant locale, std::string const& os, Minutes timezoneOffset, std::string const& accountName,
+        bgs::protocol::game_utilities::v1::ClientResponse* response) const;
 
 private:
     RealmList();