diff --git a/Lib/Core/IdCompilerDefines.inc b/Lib/Core/IdCompilerDefines.inc
index f9bc13038..2c10c4e46 100644
--- a/Lib/Core/IdCompilerDefines.inc
+++ b/Lib/Core/IdCompilerDefines.inc
@@ -1234,6 +1234,7 @@
   {$DEFINE HAS_PVOID}
   {$DEFINE HAS_ULONG64}
   {$DEFINE HAS_TEncoding_GetEncoding_ByEncodingName}
+  {$DEFINE HAS_DateUtils_TTimeZone}
   {$IFDEF DCC}
     // Exception.RaiseOuterException() is now available on all platforms
     {$DEFINE HAS_Exception_RaiseOuterException}
diff --git a/Lib/FCL/IdCompilerDefines.inc b/Lib/FCL/IdCompilerDefines.inc
index f9bc13038..2c10c4e46 100644
--- a/Lib/FCL/IdCompilerDefines.inc
+++ b/Lib/FCL/IdCompilerDefines.inc
@@ -1234,6 +1234,7 @@
   {$DEFINE HAS_PVOID}
   {$DEFINE HAS_ULONG64}
   {$DEFINE HAS_TEncoding_GetEncoding_ByEncodingName}
+  {$DEFINE HAS_DateUtils_TTimeZone}
   {$IFDEF DCC}
     // Exception.RaiseOuterException() is now available on all platforms
     {$DEFINE HAS_Exception_RaiseOuterException}
diff --git a/Lib/Protocols/IdCompilerDefines.inc b/Lib/Protocols/IdCompilerDefines.inc
index f9bc13038..2c10c4e46 100644
--- a/Lib/Protocols/IdCompilerDefines.inc
+++ b/Lib/Protocols/IdCompilerDefines.inc
@@ -1234,6 +1234,7 @@
   {$DEFINE HAS_PVOID}
   {$DEFINE HAS_ULONG64}
   {$DEFINE HAS_TEncoding_GetEncoding_ByEncodingName}
+  {$DEFINE HAS_DateUtils_TTimeZone}
   {$IFDEF DCC}
     // Exception.RaiseOuterException() is now available on all platforms
     {$DEFINE HAS_Exception_RaiseOuterException}
diff --git a/Lib/Protocols/IdFSP.pas b/Lib/Protocols/IdFSP.pas
index e7c7162d0..71a78c413 100644
--- a/Lib/Protocols/IdFSP.pas
+++ b/Lib/Protocols/IdFSP.pas
@@ -473,7 +473,7 @@ procedure ParseStatInfo(const AData : TIdBytes; VL : TIdFSPStatInfo; var VI : UI
   CopyBytesToHostUInt32(AData, VI, LC);
 
   VL.FModifiedDateGMT := UnixDateTimeToDelphiDateTime(LC);
-  VL.FModifiedDate := VL.FModifiedDateGMT + OffSetFromUTC;
+  VL.FModifiedDate := UTCTimeToLocalTime(VL.FModifiedDateGMT);
   Inc(VI, 4);
 
   CopyBytesToHostUInt32(AData, VI, LC);
diff --git a/Lib/Protocols/IdFTP.pas b/Lib/Protocols/IdFTP.pas
index fb4fa71b6..c3d90279b 100644
--- a/Lib/Protocols/IdFTP.pas
+++ b/Lib/Protocols/IdFTP.pas
@@ -4024,7 +4024,7 @@ procedure TIdFTP.SetModTime(const AFileName: String; const ALocalTime: TDateTime
   //syntax 3 - MDTM [local timestamp] Filename
   else if FTZInfo.FGMTOffsetAvailable then begin
     //send it relative to the server's time-zone
-    LCmd := 'MDTM '+ FTPDateTimeToMDTMD(ALocalTime - OffSetFromUTC + FTZInfo.FGMTOffset, False, False) + ' ' + AFileName; {do not localize}
+    LCmd := 'MDTM '+ FTPDateTimeToMDTMD(LocalTimeToUTCTime(ALocalTime) + FTZInfo.FGMTOffset, False, False) + ' ' + AFileName; {do not localize}
   end
   
   else begin
@@ -4067,7 +4067,7 @@ procedure TIdFTP.SetModTimeGMT(const AFileName : String; const AGMTTime: TDateTi
   //Syntax 2 -  MDTM yyyymmddhhmmss[+-minutes from Universal Time] Filename
   //use old method for old versions of Serv-U and BPFTP Server
   else if (IndexOfFeatLine('MDTM YYYYMMDDHHMMSS[+-TZ] filename') > 0) or IsOldServU or IsBPFTP then begin {do not localize}
-    LCmd := 'MDTM '+ FTPDateTimeToMDTMD(AGMTTime + OffSetFromUTC, False, True) + ' ' + AFileName; {do not localize}
+    LCmd := 'MDTM '+ FTPDateTimeToMDTMD(UTCTimeToLocalTime(AGMTTime), False, True) + ' ' + AFileName; {do not localize}
   end
   
   //syntax 3 - MDTM [local timestamp] Filename
@@ -4077,7 +4077,7 @@ procedure TIdFTP.SetModTimeGMT(const AFileName : String; const AGMTTime: TDateTi
   end
 
   else begin
-    LCmd := 'MDTM '+ FTPDateTimeToMDTMD(AGMTTime + OffSetFromUTC, False, False) + ' ' + AFileName; {do not localize}
+    LCmd := 'MDTM '+ FTPDateTimeToMDTMD(UTCTimeToLocalTime(AGMTTime), False, False) + ' ' + AFileName; {do not localize}
   end;
 
   // When using MDTM, Titan FTP 5 returns 200 and vsFTPd returns 213
diff --git a/Lib/Protocols/IdFTPCommon.pas b/Lib/Protocols/IdFTPCommon.pas
index 66b6c1989..6c62150b3 100644
--- a/Lib/Protocols/IdFTPCommon.pas
+++ b/Lib/Protocols/IdFTPCommon.pas
@@ -663,6 +663,7 @@ implementation
   Posix.SysTime,
   Posix.Time,
   {$ENDIF}
+  {$IFDEF HAS_DateUtils_TTimeZone}DateUtils,{$ENDIF}
   IdException;
 
 {WS_FTP Pro XAUT Support}
@@ -1219,7 +1220,7 @@ function EPLFDateToLocalDateTime(const AData: String): TDateTime;
   LSecs : Int64;
 begin
   LSecs := IndyStrToInt(AData);
-  Result := Extended( ((LSecs)/ (24 * 60 * 60) ) + Int(BASE_DATE)) - IdGlobalProtocols.TimeZoneBias;
+  Result := UTCTimeToLocalTime( Extended( ((LSecs)/ (24 * 60 * 60) ) + Int(BASE_DATE)) );
 end;
 
 function EPLFDateToGMTDateTime(const AData: String): TDateTime;
@@ -1242,7 +1243,7 @@ function GMTDateTimeToEPLFDate(const ADateTime : TDateTime) : String;
 function LocalDateTimeToEPLFDate(const ADateTime : TDateTime) : String;
   {$IFDEF USE_INLINE} inline; {$ENDIF}
 begin
-  Result := FloatToStr( Extended(ADateTime + IdGlobalProtocols.TimeZoneBias - Int(EPLF_BASE_DATE)) * 24 * 60 * 60);
+  Result := FloatToStr( Extended( LocalTimeToUTCTime(ADateTime) - Int(EPLF_BASE_DATE)) * 24 * 60 * 60);
 end;
 
 {Date routines}
@@ -1343,11 +1344,27 @@ function MDTMOffset(const AOffs : String) : TDateTime;
 end;
 
 function MinutesFromGMT : Integer;
+{$IFDEF HAS_GetLocalTimeOffset}
   {$IFDEF USE_INLINE} inline; {$ENDIF}
+{$ELSE}
+  {$IFDEF HAS_DateUtils_TTimeZone}
+    {$IFDEF USE_INLINE} inline; {$ENDIF}
+  {$ELSE}
 var
   LD : TDateTime;
   LHour, LMin, LSec, LMSec : Word;
+  {$ENDIF}
+{$ENDIF}
 begin
+  {$IFDEF HAS_GetLocalTimeOffset}
+  // RLebeau: Note that on Linux/Unix, this information may be inaccurate around
+  // the DST time changes (for optimization). In that case, the unix.ReReadLocalTime()
+  // function must be used to re-initialize the timezone information...
+  Result := {-1 *} GetLocalTimeOffset();
+  {$ELSE}
+    {$IFDEF HAS_DateUtils_TTimeZone}
+  Result := {-1 *} TTimeZone.Local.UtcOffset.TotalMinutes;
+    {$ELSE}
   LD := OffsetFromUTC;
   DecodeTime(LD, LHour, LMin, LSec, LMSec);
   if LD < 0.0 then begin
@@ -1355,6 +1372,8 @@ function MinutesFromGMT : Integer;
   end else begin
     Result := LHour * 60 + LMin;
   end;
+    {$ENDIF}
+  {$ENDIF}
 end;
 
 function FTPDateTimeToMDTMD(const ATimeStamp : TDateTime; const AIncludeMSecs : Boolean=True; const AIncludeGMTOffset : Boolean=True): String;
@@ -1415,7 +1434,7 @@ function FTPMDTMToGMTDateTime(const ATimeStamp : String):TDateTime;
       Result := EncodeDate(LYear, LMonth, LDay);
       Result := Result + EncodeTime(LHour, LMin, LSec, LMSec);
       if LOffset = '' then begin
-        Result := Result - OffsetFromUTC;
+        Result := LocalTimeToUTCTime(Result);
       end else begin
         Result := Result - MDTMOffset(LOffset);
       end;
diff --git a/Lib/Protocols/IdFTPListOutput.pas b/Lib/Protocols/IdFTPListOutput.pas
index e62c582d3..53f891b45 100644
--- a/Lib/Protocols/IdFTPListOutput.pas
+++ b/Lib/Protocols/IdFTPListOutput.pas
@@ -596,7 +596,7 @@ function TIdFTPListOutput.GetItems(AIndex: Integer): TIdFTPListOutputItem;
 function TIdFTPListOutput.GetLocalModTime(AItem: TIdFTPListOutputItem): TDateTime;
 begin
   if AItem.ModifiedDateGMT <> 0 then begin
-    Result := AItem.ModifiedDateGMT - TimeZoneBias;
+    Result := UTCTimeToLocalTime(AItem.ModifiedDateGMT);
   end else begin
     Result := AItem.ModifiedDate;
   end;
diff --git a/Lib/Protocols/IdFTPListParseDistinctTCPIP.pas b/Lib/Protocols/IdFTPListParseDistinctTCPIP.pas
index 5dc4d648b..2e78e05ee 100644
--- a/Lib/Protocols/IdFTPListParseDistinctTCPIP.pas
+++ b/Lib/Protocols/IdFTPListParseDistinctTCPIP.pas
@@ -193,7 +193,7 @@ class function TIdFTPLPDistinctTCPIP.ParseLine(const AItem: TIdFTPListItem;
   // 12/29/2002  01:42p                  23 CreateTest.txt
   // I suspect that this server returns the timestamp as GMT
   LI.ModifiedDateGMT := LI.ModifiedDate;
-  LI.ModifiedDate := LI.ModifiedDate - TimeZoneBias;
+  LI.ModifiedDate := UTCTimeToLocalTime(LI.ModifiedDateGMT);
   // file name
   LBuf := StripSpaces(LBuf, 1);
   LI.FileName := LBuf;
diff --git a/Lib/Protocols/IdFTPServer.pas b/Lib/Protocols/IdFTPServer.pas
index f6f128ad8..e8f0e1c80 100644
--- a/Lib/Protocols/IdFTPServer.pas
+++ b/Lib/Protocols/IdFTPServer.pas
@@ -5312,7 +5312,7 @@ procedure TIdFTPServer.DoOnGetFileDate(ASender: TIdFTPServerContext;
   LFileSystem := FTPFileSystem;
   if Assigned(LFileSystem) then begin
     LFileSystem.GetFileDate(ASender, AFileName, VFileDate);
-	  VFileDate := VFileDate - OffsetFromUTC;
+    VFileDate := LocalTimeToUTCTime(VFileDate);
   end else if Assigned(FOnGetFileDate) then begin
     FOnGetFileDate(ASender, AFileName, VFileDate);
   end;
@@ -5477,7 +5477,7 @@ procedure TIdFTPServer.CommandSiteUTIME(ASender: TIdCommand);
     if IsValidTimeStamp(ALSender.Params[0]) then begin
       LFileName := ALSender.UnparsedParams;
       //This is local Time
-      LgMTime := FTPMLSToGMTDateTime(Fetch(LFileName)) - OffsetFromUTC;
+      LgMTime := UTCTimeToLocalTime(FTPMLSToGMTDateTime(Fetch(LFileName)));
       LFileName := DoProcessPath(AContext, LFileName);
       if Assigned(FOnSiteUTIME) then
       begin
@@ -6200,14 +6200,16 @@ procedure TIdFTPServer.CommandCPSV(ASender: TIdCommand);
 procedure TIdFTPServer.CommandSiteZONE(ASender: TIdCommand);
 var
   LMin : Integer;
+  LFmt: string;
 begin
   LMin := MinutesFromGMT;
   //plus must always be displayed for positive numbers
   if LMin < 0 then begin
-    ASender.Reply.SetReply(210, IndyFormat('UTC%d', [MinutesFromGMT])); {do not localize}
+    LFmt := 'UTC%d'; {do not localize}
   end else begin
-    ASender.Reply.SetReply(210, IndyFormat('UTC+%d', [MinutesFromGMT])); {do not localize}
+    LFmt := 'UTC+%d'; {do not localize}
   end;
+  ASender.Reply.SetReply(210, IndyFormat(LFmt, [LMin]));
 end;
 
 procedure TIdFTPServer.CommandCheckSum(ASender: TIdCommand);
diff --git a/Lib/Protocols/IdGlobalProtocols.pas b/Lib/Protocols/IdGlobalProtocols.pas
index c7e29101f..a5cb2c50e 100644
--- a/Lib/Protocols/IdGlobalProtocols.pas
+++ b/Lib/Protocols/IdGlobalProtocols.pas
@@ -523,7 +523,7 @@   EIdExtensionAlreadyExists = class(EIdException);
   function StrToDay(const ADay: string): Byte;
   function StrToMonth(const AMonth: string): Byte;
   function StrToWord(const Value: String): Word;
-  function TimeZoneBias: TDateTime;
+  function TimeZoneBias: TDateTime; {$IFDEF HAS_DEPRECATED}deprecated{$IFDEF HAS_DEPRECATED_MSG} 'Use IdGlobal.LocalTimeToUTCTime() or IdGlobal.UTCTimeToLocalTime()'{$ENDIF};{$ENDIF}
    //these are for FSP but may also help with MySQL
   function UnixDateTimeToDelphiDateTime(UnixDateTime: UInt32): TDateTime;
   function DateTimeToUnix(ADateTime: TDateTime): UInt32;
@@ -593,14 +593,8 @@ implementation
     {$ENDIF}
   {$ENDIF}
   IdIPAddress,
-  {$IFDEF HAS_GetLocalTimeOffset}
-  DateUtils,
-  {$ENDIF}
   {$IFDEF UNIX}
     {$IFDEF USE_VCL_POSIX}
-      {$IFNDEF HAS_GetLocalTimeOffset}
-  DateUtils,
-      {$ENDIF}
   Posix.SysStat, Posix.SysTime, Posix.Time, Posix.Unistd,
     {$ELSE}
       {$IFDEF KYLIXCOMPAT}
@@ -608,13 +602,13 @@ implementation
       {$ELSE}
         {$IFDEF USE_BASEUNIX}
   BaseUnix, Unix,
-          {$IFNDEF HAS_GetLocalTimeOffset}
-  DateUtils,
-          {$ENDIF}
         {$ENDIF}
       {$ENDIF}
     {$ENDIF}
   {$ENDIF}
+  {$IFDEF HAS_UNIT_DateUtils}
+  DateUtils,
+  {$ENDIF}
   {$IFDEF WINDOWS}
   Messages,
   Registry,
@@ -1352,7 +1346,7 @@ function FTPMLSToLocalDateTime(const ATimeStamp : String):TDateTime;
   if ATimeStamp <> '' then begin
     Result := FTPMLSToGMTDateTime(ATimeStamp);
     // Apply local offset
-    Result := {$IFDEF HAS_UniversalTimeToLocal}UniversalTimeToLocal(Result){$ELSE}Result + OffsetFromUTC{$ENDIF};
+    Result := UTCTimeToLocalTime(Result);
   end;
 end;
 
@@ -1378,13 +1372,7 @@ function FTPGMTDateTimeToMLS(const ATimeStamp : TDateTime; const AIncludeMSecs :
 function FTPLocalDateTimeToMLS(const ATimeStamp : TDateTime; const AIncludeMSecs : Boolean=True): String;
 {$IFDEF USE_INLINE} inline; {$ENDIF}
 begin
-  Result := FTPGMTDateTimeToMLS(
-    {$IFDEF HAS_LocalTimeToUniversal}
-    LocalTimeToUniversal(ATimeStamp)
-    {$ELSE}
-    ATimeStamp - OffsetFromUTC
-    {$ENDIF}
-    , AIncludeMSecs);
+  Result := FTPGMTDateTimeToMLS(LocalTimeToUTCTime(ATimeStamp), AIncludeMSecs);
 end;
 
 
@@ -1981,36 +1969,12 @@ function RightStr(const AStr: String; const Len: Integer): String;
   end;
 end;
 
+{$I IdDeprecatedImplBugOff.inc}
 function TimeZoneBias: TDateTime;
-{$IFNDEF FPC}
-  {$IFDEF UNIX}
-var
-  T: Time_T;
-  TV: TimeVal;
-  UT: {$IFDEF USE_VCL_POSIX}tm{$ELSE}TUnixTime{$ENDIF};
-  {$ELSE}
-    {$IFDEF USE_INLINE} inline; {$ENDIF}
-  {$ENDIF}
-{$ELSE}
+{$I IdDeprecatedImplBugOn.inc}
   {$IFDEF USE_INLINE} inline; {$ENDIF}
-{$ENDIF}
 begin
-{$IFNDEF FPC}
-  {$IFDEF UNIX}
-  // TODO: use -OffsetFromUTC here. It has this same Unix logic in it
-  {from http://edn.embarcadero.com/article/27890 }
-  gettimeofday(TV, nil);
-  T := TV.tv_sec;
-  localtime_r({$IFNDEF USE_VCL_POSIX}@{$ENDIF}T, UT);
-// __tm_gmtoff is the bias in seconds from the UTC to the current time.
-// so I multiply by -1 to compensate for this.
-  Result := (UT.{$IFNDEF USE_VCL_POSIX}__tm_gmtoff{$ELSE}tm_gmtoff{$ENDIF} / 60 / 60 / 24);
-  {$ELSE}
-  Result := -OffsetFromUTC;
-  {$ENDIF}
-{$ELSE}
   Result := -OffsetFromUTC;
-{$ENDIF}
 end;
 
 function IndyStrToBool(const AString : String) : Boolean;
@@ -2810,8 +2774,7 @@ function GMTToLocalDateTime(S: string): TDateTime;
   if RawStrInternetToDateTime(S, Result) then begin
     DateTimeOffset := GmtOffsetStrToDateTime(S);
     {-Apply GMT and local offsets}
-    Result := Result - DateTimeOffset;
-    Result := {$IFDEF HAS_UniversalTimeToLocal}UniversalTimeToLocal(Result){$ELSE}Result + OffsetFromUTC{$ENDIF};
+    Result := UTCTimeToLocalTime(Result - DateTimeOffset);
   end;
 end;
 
@@ -3066,7 +3029,7 @@ function CookieStrToLocalDateTime(S: string): TDateTime;
     end;
 
     Result := EncodeDate(LYear, LMonth, LDayOfMonth) + EncodeTime(LHour, LMinute, LSecond, 0);
-    Result := {$IFDEF HAS_UniversalTimeToLocal}UniversalTimeToLocal(Result){$ELSE}Result + OffsetFromUTC{$ENDIF};
+    Result := UTCTimeToLocalTime(Result);
   except
     Result := 0.0;
   end;
diff --git a/Lib/Protocols/IdHTTPWebBrokerBridge.pas b/Lib/Protocols/IdHTTPWebBrokerBridge.pas
index df14e7077..c7b5ca0e4 100644
--- a/Lib/Protocols/IdHTTPWebBrokerBridge.pas
+++ b/Lib/Protocols/IdHTTPWebBrokerBridge.pas
@@ -628,7 +628,7 @@ function TIdHTTPAppResponse.GetDateVariable(Index: Integer): TDateTime;
   begin
     Result := ADateTime;
     if Result <> -1 then
-      Result := Result - OffsetFromUTC;
+      Result := LocalTimeToUTCTime(Result);
   end;
 begin
   //TODO: resource string these
@@ -647,7 +647,7 @@ procedure TIdHTTPAppResponse.SetDateVariable(Index: Integer; const Value: TDateT
   begin
     Result := ADateTime;
     if Result <> -1 then
-      Result := Result + OffsetFromUTC;
+      Result := UTCTimeToLocalTime(Result);
   end;
 begin
   //TODO: resource string these
diff --git a/Lib/Protocols/IdNNTPServer.pas b/Lib/Protocols/IdNNTPServer.pas
index 47a4e5bd6..d1f0ca978 100644
--- a/Lib/Protocols/IdNNTPServer.pas
+++ b/Lib/Protocols/IdNNTPServer.pas
@@ -463,7 +463,7 @@ class function TIdNNTPServer.NNTPTimeToTime(const ATimeStamp : String): TDateTim
     if TextIsSame(LTimeStr, 'GMT') then  {do not localize}
     begin
       // Apply local offset
-      Result := Result + OffsetFromUTC;
+      Result := UTCTimeToLocalTime(Result);
     end;
   end else begin
     Result := 0.0;
@@ -652,7 +652,7 @@ procedure TIdNNTPServer.CommandBody(ASender: TIdCommand);
 procedure TIdNNTPServer.CommandDate(ASender: TIdCommand);
 begin
   if not SecLayerRequired(ASender) then begin
-    ASender.Reply.SetReply(111, FormatDateTime('yyyymmddhhnnss', Now + TimeZoneBias));  {do not localize}
+    ASender.Reply.SetReply(111, FormatDateTime('yyyymmddhhnnss', LocalTimeToUTCTime(Now)));  {do not localize}
   end;
 end;
 
@@ -1551,7 +1551,7 @@ procedure TIdNNTPServer.CommandNewGroups(ASender: TIdCommand);
         LDate := LDate + NNTPTimeToTime(ASender.Params[1]);
         if ASender.Params.Count > 2 then begin
           if TextIsSame(ASender.Params[2], 'GMT') then begin {Do not translate}
-            LDate := LDate + OffSetFromUTC;
+            LDate := UTCTimeToLocalTime(LDate);
             if ASender.Params.Count > 3 then begin
               LDist := ASender.Params[3];
             end;
@@ -1587,7 +1587,7 @@ procedure TIdNNTPServer.CommandNewNews(ASender: TIdCommand);
         LDate := LDate + NNTPTimeToTime(ASender.Params[2]);
         if ASender.Params.Count > 3 then begin
           if TextIsSame(ASender.Params[3], 'GMT') then begin {Do not translate}
-            LDate := LDate + OffsetFromUTC;
+            LDate := UTCTimeToLocalTime(LDate);
             if ASender.Params.Count > 4 then begin
               LDist := ASender.Params[4];
             end;
diff --git a/Lib/Protocols/IdSNTP.pas b/Lib/Protocols/IdSNTP.pas
index 0f55144d8..e32f1cabb 100644
--- a/Lib/Protocols/IdSNTP.pas
+++ b/Lib/Protocols/IdSNTP.pas
@@ -149,7 +149,7 @@ procedure TIdSNTP.DateTimeToNTP(ADateTime: TDateTime; var Second, Fraction: UInt
 var
   Value1, Value2: Double;
 begin
-  Value1 := (ADateTime + TimeZoneBias - 2) * 86400;
+  Value1 := (LocalTimeToUTCTime(ADateTime) - 2) * 86400;
   Value2 := Value1;
 
   if Value2 > NTPMaxInt then
@@ -191,7 +191,7 @@ function TIdSNTP.NTPToDateTime(Second, Fraction: UInt32): TDateTime;
   // Value2 := Trunc(Value2 * 1000) / 1000;
 
   Value2 := Trunc(Value2 / NTPMaxInt * 1000) / 1000;
-  Result := ((Value1 + Value2) / 86400) - TimeZoneBias + 2;
+  Result := UTCTimeToLocalTime((Value1 + Value2) / 86400) + 2;
 end ;
 
 { TIdSNTP }
@@ -232,6 +232,7 @@ function TIdSNTP.GetDateTime: TDateTime;
 var
   LNTPDataGram: TNTPGram;
   LBuffer : TIdBytes;
+  LBytesRecvd: Integer;
 begin
   // DS default result is an empty TDateTime value
   Result := 0.0;
@@ -245,10 +246,10 @@ function TIdSNTP.GetDateTime: TDateTime;
   CopyTIdUInt32(GStack.HostToNetwork(LNTPDataGram.Xmit2), LBuffer, 44);
 
   SendBuffer(LBuffer);
-  ReceiveBuffer(LBuffer);
+  LBytesRecvd := ReceiveBuffer(LBuffer);
 
   // DS response may contain optional NTP authentication scheme info not in NTPGram
-  if Length(LBuffer) >= SizeOf(TNTPGram) then
+  if LBytesRecvd >= SizeOf(TNTPGram) then
   begin
     FDestinationTimeStamp := Now;
 
diff --git a/Lib/Protocols/IdSSLOpenSSL.pas b/Lib/Protocols/IdSSLOpenSSL.pas
index 69f2c688e..ed556c291 100644
--- a/Lib/Protocols/IdSSLOpenSSL.pas
+++ b/Lib/Protocols/IdSSLOpenSSL.pas
@@ -2131,12 +2131,6 @@ function AddHrs(const DT: TDateTime; const Hrs: Extended): TDateTime;
   Result := DT + Hrs / 24.0;
 end;
 
-function GetLocalTime(const DT: TDateTime): TDateTime;
-{$IFDEF USE_INLINE} inline; {$ENDIF}
-begin
-  Result := DT - TimeZoneBias { / (24 * 60) } ;
-end;
-
 {$IFDEF OPENSSL_SET_MEMORY_FUNCS}
 
 function IdMalloc(num: UInt32): Pointer cdecl;
@@ -2287,12 +2281,11 @@ function UTCTime2DateTime(UCTTime: PASN1_UTCTIME): TDateTime;
   tz_m: Integer;
 begin
   Result := 0;
-  if UTC_Time_Decode(UCTTime, year, month, day, hour, min, sec, tz_h,
-    tz_m) > 0 then begin
+  if UTC_Time_Decode(UCTTime, year, month, day, hour, min, sec, tz_h, tz_m) > 0 then begin
     Result := EncodeDate(year, month, day) + EncodeTime(hour, min, sec, 0);
     AddMins(Result, tz_m);
     AddHrs(Result, tz_h);
-    Result := GetLocalTime(Result);
+    Result := UTCTimeToLocalTime(Result);
   end;
 end;
 
diff --git a/Lib/Protocols/IdSSLOpenSSLUtils.pas b/Lib/Protocols/IdSSLOpenSSLUtils.pas
index 314a590ed..3ef8f2891 100644
--- a/Lib/Protocols/IdSSLOpenSSLUtils.pas
+++ b/Lib/Protocols/IdSSLOpenSSLUtils.pas
@@ -40,7 +40,7 @@ procedure LockVerifyCB_Leave;
 //
 function AddMins(const DT: TDateTime; const Mins: Extended): TDateTime;
 function AddHrs(const DT: TDateTime; const Hrs: Extended): TDateTime;
-function GetLocalTime(const DT: TDateTime): TDateTime;
+function GetLocalTime(const DT: TDateTime): TDateTime; {$IFDEF HAS_DEPRECATED}deprecated{$IFDEF HAS_DEPRECATED_MSG} 'Use IdGlobal.UTCTimeToLocalTime()'{$ENDIF};{$ENDIF}
 
 function IndySSL_load_client_CA_file(const AFileName: String) : PSTACK_OF_X509_NAME;
 function IndySSL_CTX_use_PrivateKey_file(ctx: PSSL_CTX; const AFileName: String;
@@ -673,10 +673,12 @@ function AddHrs(const DT: TDateTime; const Hrs: Extended): TDateTime;
   Result := DT + Hrs / 24.0;
 end;
 
+{$I IdDeprecatedImplBugOff.inc}
 function GetLocalTime(const DT: TDateTime): TDateTime;
+{$I IdDeprecatedImplBugOn.inc}
 {$IFDEF USE_INLINE} inline; {$ENDIF}
 begin
-  Result := DT - TimeZoneBias { / (24 * 60) } ;
+  Result := UTCTimeToLocalTime(DT);
 end;
 
 {$IFDEF OPENSSL_SET_MEMORY_FUNCS}
diff --git a/Lib/Protocols/IdTime.pas b/Lib/Protocols/IdTime.pas
index 721701ea5..a8bf726e6 100644
--- a/Lib/Protocols/IdTime.pas
+++ b/Lib/Protocols/IdTime.pas
@@ -176,8 +176,7 @@ function TIdCustomTime.GetDateTime: TDateTime;
   if BufCard <> 0 then begin
     {The formula is The Time cardinal we receive divided by (24 * 60*60 for days + RoundTrip divided by one-thousand since this is based on seconds
     - the Time Zone difference}
-    Result := ( ((BufCard + (FRoundTripDelay div 1000))/ (24 * 60 * 60) ) + Int(fBaseDate))
-    -TimeZoneBias;
+    Result := UTCTimeToLocalTime( ((BufCard + (FRoundTripDelay div 1000))/ (24 * 60 * 60) ) + Int(fBaseDate) );
 
   end else begin
     { Somehow, I really doubt we are ever going to really get a time such as
diff --git a/Lib/Protocols/IdTimeServer.pas b/Lib/Protocols/IdTimeServer.pas
index 2acdfd62c..501b96f99 100644
--- a/Lib/Protocols/IdTimeServer.pas
+++ b/Lib/Protocols/IdTimeServer.pas
@@ -135,7 +135,7 @@ procedure TIdCustomTimeServer.InitComponent;
 function TIdCustomTimeServer.DoExecute(AContext: TIdContext): Boolean;
 begin
   Result := true;
-  AContext.Connection.IOHandler.Write(UInt32(Trunc(Extended(Now + TimeZoneBias - Int(FBaseDate)) * 24 * 60 * 60)));
+  AContext.Connection.IOHandler.Write(UInt32(Trunc(Extended(LocalTimeToUTCTime(Now) - Int(FBaseDate)) * 24 * 60 * 60)));
   AContext.Connection.Disconnect;
 end;
 
diff --git a/Lib/Protocols/IdTimeUDP.pas b/Lib/Protocols/IdTimeUDP.pas
index 209e9c90a..305ba52cf 100644
--- a/Lib/Protocols/IdTimeUDP.pas
+++ b/Lib/Protocols/IdTimeUDP.pas
@@ -127,8 +127,7 @@ function TIdCustomTimeUDP.GetDateTime: TDateTime;
   if BufCard <> 0 then begin
     {The formula is The Time cardinal we receive divided by (24 * 60*60 for days + RoundTrip divided by one-thousand since this is based on seconds
     - the Time Zone difference}
-    Result := ( ((BufCard + (FRoundTripDelay div 1000))/ (24 * 60 * 60) ) + Int(fBaseDate))
-                - TimeZoneBias;
+    Result := UTCTimeToLocalTime( ((BufCard + (FRoundTripDelay div 1000))/ (24 * 60 * 60) ) + Int(fBaseDate) );
   end else begin
     { Somehow, I really doubt we are ever going to really get a time such as
     12/30/1899 12:00 am so use that as a failure test}
diff --git a/Lib/Protocols/IdTimeUDPServer.pas b/Lib/Protocols/IdTimeUDPServer.pas
index 71868d14d..f58774d26 100644
--- a/Lib/Protocols/IdTimeUDPServer.pas
+++ b/Lib/Protocols/IdTimeUDPServer.pas
@@ -97,7 +97,7 @@ procedure TIdCustomTimeUDPServer.DoUDPRead(AThread: TIdUDPListenerThread;
   LTime : UInt32;
 begin
   inherited DoUDPRead(AThread, AData, ABinding);
-  LTime := Trunc(Extended(Now + TimeZoneBias - Int(FBaseDate)) * 24 * 60 * 60);
+  LTime := Trunc(Extended(LocalTimeToUTCTime(Now) - Int(FBaseDate)) * 24 * 60 * 60);
   LTime := GStack.HostToNetwork(LTime);
   ABinding.SendTo(ABinding.PeerIP, ABinding.PeerPort, ToBytes(LTime), ABinding.IPVersion);
 end;
diff --git a/Lib/SuperCore/IdCompilerDefines.inc b/Lib/SuperCore/IdCompilerDefines.inc
index f9bc13038..2c10c4e46 100644
--- a/Lib/SuperCore/IdCompilerDefines.inc
+++ b/Lib/SuperCore/IdCompilerDefines.inc
@@ -1234,6 +1234,7 @@
   {$DEFINE HAS_PVOID}
   {$DEFINE HAS_ULONG64}
   {$DEFINE HAS_TEncoding_GetEncoding_ByEncodingName}
+  {$DEFINE HAS_DateUtils_TTimeZone}
   {$IFDEF DCC}
     // Exception.RaiseOuterException() is now available on all platforms
     {$DEFINE HAS_Exception_RaiseOuterException}
diff --git a/Lib/System/IdCompilerDefines.inc b/Lib/System/IdCompilerDefines.inc
index f9bc13038..2c10c4e46 100644
--- a/Lib/System/IdCompilerDefines.inc
+++ b/Lib/System/IdCompilerDefines.inc
@@ -1234,6 +1234,7 @@
   {$DEFINE HAS_PVOID}
   {$DEFINE HAS_ULONG64}
   {$DEFINE HAS_TEncoding_GetEncoding_ByEncodingName}
+  {$DEFINE HAS_DateUtils_TTimeZone}
   {$IFDEF DCC}
     // Exception.RaiseOuterException() is now available on all platforms
     {$DEFINE HAS_Exception_RaiseOuterException}
diff --git a/Lib/System/IdGlobal.pas b/Lib/System/IdGlobal.pas
index f4d4ae883..2692003f5 100644
--- a/Lib/System/IdGlobal.pas
+++ b/Lib/System/IdGlobal.pas
@@ -1865,6 +1865,9 @@ function MemoryPos(const ASubStr: string; MemBuff: PChar; MemorySize: Integer):
 function OffsetFromUTC: TDateTime;
 function UTCOffsetToStr(const AOffset: TDateTime; const AUseGMTStr: Boolean = False): string;
 
+function LocalTimeToUTCTime(const Value: TDateTime): TDateTime;
+function UTCTimeToLocalTime(const Value: TDateTime): TDateTime;
+
 function PosIdx(const ASubStr, AStr: string; AStartPos: UInt32 = 0): UInt32; //For "ignoreCase" use AnsiUpperCase
 function PosInSmallIntArray(const ASearchInt: Int16; const AArray: array of Int16): Integer;
 function PosInStrArray(const SearchStr: string; const Contents: array of string; const CaseSensitive: Boolean = True): Integer;
@@ -7754,37 +7757,19 @@ function DateTimeGMTToImapStr(const GMTValue: TDateTime) : String;
 function LocalDateTimeToHttpStr(const Value: TDateTime) : String;
 {$IFDEF USE_INLINE}inline;{$ENDIF}
 begin
-  Result := DateTimeGMTToHttpStr(
-    {$IFDEF HAS_LocalTimeToUniversal}
-    LocalTimeToUniversal(Value)
-    {$ELSE}
-    Value - OffsetFromUTC
-    {$ENDIF}
-  );
+  Result := DateTimeGMTToHttpStr(LocalTimeToUTCTime(Value));
 end;
 
 function LocalDateTimeToCookieStr(const Value: TDateTime; const AUseNetscapeFmt: Boolean = True) : String;
 {$IFDEF USE_INLINE}inline;{$ENDIF}
 begin
-  Result := DateTimeGMTToCookieStr(
-    {$IFDEF HAS_LocalTimeToUniversal}
-    LocalTimeToUniversal(Value)
-    {$ELSE}
-    Value - OffsetFromUTC
-    {$ENDIF}
-    , AUseNetscapeFmt);
+  Result := DateTimeGMTToCookieStr(LocalTimeToUTCTime(Value), AUseNetscapeFmt);
 end;
 
 function LocalDateTimeToImapStr(const Value: TDateTime) : String;
 {$IFDEF USE_INLINE}inline;{$ENDIF}
 begin
-  Result := DateTimeGMTToImapStr(
-    {$IFDEF HAS_LocalTimeToUniversal}
-    LocalTimeToUniversal(Value)
-    {$ELSE}
-    Value - OffsetFromUTC
-    {$ENDIF}
-  );
+  Result := DateTimeGMTToImapStr(LocalTimeToUTCTime(Value));
 end;
 
 {$I IdDeprecatedImplBugOff.inc}
@@ -7852,7 +7837,16 @@ function OffsetFromUTC: TDateTime;
   {$IFDEF DOTNET}
   Result := System.Timezone.CurrentTimezone.GetUTCOffset(DateTime.FromOADate(Now)).TotalDays;
   {$ELSE}
-    {$IFDEF WINDOWS}
+    {$IFDEF HAS_GetLocalTimeOffset}
+  // RLebeau: Note that on Linux/Unix, this information may be inaccurate around
+  // the DST time changes (for optimization). In that case, the unix.ReReadLocalTime()
+  // function must be used to re-initialize the timezone information...
+  Result := GetLocalTimeOffset() / 60 / 24;
+    {$ELSE}
+      {$IFDEF HAS_DateUtils_TTimeZone}
+  Result := TTimeZone.Local.UtcOffset.TotalMinutes / 60 / 24;
+      {$ELSE}
+        {$IFDEF WINDOWS}
   case GetTimeZoneInformation({$IFDEF WINCE}@{$ENDIF}tmez) of
     TIME_ZONE_ID_INVALID  :
       raise EIdFailedToRetreiveTimeZoneInfo.Create(RSFailedTimeZoneInfo);
@@ -7884,37 +7878,32 @@ function OffsetFromUTC: TDateTime;
   if iBias > 0 then begin
     Result := 0.0 - Result;
   end;
-    {$ELSE}
-      {$IFDEF HAS_GetLocalTimeOffset}
-  // RLebeau: Note that on Linux/Unix, this information may be inaccurate around
-  // the DST time changes (for optimization). In that case, the unix.ReReadLocalTime()
-  // function must be used to re-initialize the timezone information...
-  Result := -1 * (GetLocalTimeOffset() / 60 / 24);
-      {$ELSE}
-        {$IFDEF UNIX}
+        {$ELSE}
+          {$IFDEF UNIX}
 
   // TODO: raise EIdFailedToRetreiveTimeZoneInfo if gettimeofday() fails...
 
-          {$IFDEF KYLIXCOMPAT_OR_VCL_POSIX}
+            {$IFDEF KYLIXCOMPAT_OR_VCL_POSIX}
   {from http://edn.embarcadero.com/article/27890 but without multiplying the Result by -1}
 
   gettimeofday(TV, nil);
   T := TV.tv_sec;
   localtime_r({$IFDEF KYLIXCOMPAT}@{$ENDIF}T, UT);
   Result := UT.{$IFDEF KYLIXCOMPAT}__tm_gmtoff{$ELSE}tm_gmtoff{$ENDIF} / 60 / 60 / 24;
-          {$ELSE}
-            {$IFDEF USE_BASEUNIX}
+            {$ELSE}
+              {$IFDEF USE_BASEUNIX}
   fpGetTimeOfDay (@TimeVal, @TimeZone);
   Result := -1 * (timezone.tz_minuteswest / 60 / 24);
-            {$ELSE}
+              {$ELSE}
   {$message error gettimeofday is not called on this platform!}
   Result := GOffsetFromUTC;
+              {$ENDIF}
             {$ENDIF}
-          {$ENDIF}
 
-        {$ELSE}
+          {$ELSE}
   {$message error no platform API called to get UTC offset!}
   Result := GOffsetFromUTC;
+          {$ENDIF}
         {$ENDIF}
       {$ENDIF}
     {$ENDIF}
@@ -7956,6 +7945,32 @@ function UTCOffsetToStr(const AOffset: TDateTime; const AUseGMTStr: Boolean = Fa
   end;
 end;
 
+function LocalTimeToUTCTime(const Value: TDateTime): TDateTime;
+begin
+  {$IFDEF HAS_LocalTimeToUniversal}
+  Result := LocalTimeToUniversal(Value);
+  {$ELSE}
+    {$IFDEF HAS_DateUtils_TTimeZone}
+  Result := TTimeZone.Local.ToUniversalTime(Value);
+    {$ELSE}
+  Result := Value - OffsetFromUTC;
+    {$ENDIF}
+  {$ENDIF}
+end;
+
+function UTCTimeToLocalTime(const Value: TDateTime): TDateTime;
+begin
+  {$IFDEF HAS_UniversalTimeToLocal}
+  Result := UniversalTimeToLocal(Value);
+  {$ELSE}
+    {$IFDEF HAS_DateUtils_TTimeZone}
+  Result := TTimeZone.Local.ToLocalTime(Value);
+    {$ELSE}
+  Result := Value + OffsetFromUTC;
+    {$ENDIF}
+  {$ENDIF}
+end;
+
 function IndyIncludeTrailingPathDelimiter(const S: string): string;
 {$IFDEF USE_INLINE}inline;{$ENDIF}
 begin