* Extend GetLocalTimeOffset to return Dst or not

rtl/objpas/sysutils/dati.inc

@@ -1613,7 +1613,7 @@ begin
   Result:=0;
 end;
 
-function GetLocalTimeOffset(const DateTime: TDateTime; const InputIsUTC: Boolean; out Offset: Integer): Boolean;
+function GetLocalTimeOffset(const DateTime: TDateTime; const InputIsUTC: Boolean; out Offset: Integer; out isDST : Boolean): Boolean;
 begin
   Result:=False;
 end;
@@ -1624,9 +1624,21 @@ begin
 end;
 {$ENDIF}
 
+function GetLocalTimeOffset(const DateTime: TDateTime; const InputIsUTC: Boolean; out Offset: Integer): Boolean;
+
+var
+  dst : Boolean;
+
+begin
+  Result:=GetLocalTimeOffset(DateTime,InputIsUTC,Offset,dst);
+end;
+
+
 function GetLocalTimeOffset(const DateTime: TDateTime; const InputIsUTC: Boolean): Integer;
+var
+  dst : Boolean;
 begin
-  if not GetLocalTimeOffset(DateTime, InputIsUTC, Result) then
+  if not GetLocalTimeOffset(DateTime, InputIsUTC, Result,dst) then
     Result:=GetLocalTimeOffset();
 end;
 

rtl/objpas/sysutils/datih.inc

@@ -209,6 +209,7 @@ procedure ReplaceDate(var DateTime: TDateTime; const NewDate: TDateTime); inline
 
 function GetLocalTimeOffset: Integer;
 function GetLocalTimeOffset(const DateTime: TDateTime; const InputIsUTC: Boolean; out Offset: Integer): Boolean;
+function GetLocalTimeOffset(const DateTime: TDateTime; const InputIsUTC: Boolean; out Offset: Integer; out IsDST : Boolean): Boolean;
 function GetLocalTimeOffset(const DateTime: TDateTime; const InputIsUTC: Boolean = False): Integer;
 
 { UTC <-> Local time }

rtl/objpas/sysutils/tzenv.inc

@@ -914,12 +914,13 @@ end;
 {$ENDIF HAS_DUAL_TZHANDLING}
 
 
-function GetLocalTimeOffset(const DateTime: TDateTime; const InputIsUTC: boolean; out Offset: integer): boolean;
+function GetLocalTimeOffset(const DateTime: TDateTime; const InputIsUTC: boolean; out Offset: integer; out isDST : Boolean): boolean;
 var
   SystemTime: TSystemTime;
 begin
   DateTimeToSystemTime (DateTime, SystemTime);
-  if InDST (SystemTime, InputIsUTC) then
+  isDST:=InDST (SystemTime, InputIsUTC);
+  if isDST then
    Offset := DSTOffsetMin
   else
    Offset := TZOffsetMin;

rtl/unix/sysutils.pp

@@ -1886,7 +1886,8 @@ begin
  Result := -Tzseconds div 60; 
 end;
 
-function GetLocalTimeOffset(const DateTime: TDateTime; const InputIsUTC: Boolean; out Offset: Integer): Boolean;
+
+function GetLocalTimeOffset(const DateTime: TDateTime; const InputIsUTC: Boolean; out Offset: Integer; out IsDST : Boolean): Boolean;
 
 var
   Year, Month, Day, Hour, Minute, Second, MilliSecond: word;
@@ -1896,9 +1897,9 @@ begin
   DecodeDate(DateTime, Year, Month, Day);
   DecodeTime(DateTime, Hour, Minute, Second, MilliSecond);
   UnixTime:=UniversalToEpoch(Year, Month, Day, Hour, Minute, Second);
-
   {$if declared(GetLocalTimezone)}
   GetLocalTimeOffset:=GetLocalTimezone(UnixTime,InputIsUTC,lTZInfo);
+  isDST:=lTZInfo.daylight;
   if GetLocalTimeOffset then
     Offset:=-lTZInfo.seconds div 60;
   {$else}

rtl/win/sysutils.pp

@@ -992,7 +992,7 @@ type
 var
   GetTimeZoneInformationForYear:TGetTimeZoneInformationForYear=nil;
 
-function GetLocalTimeOffset(const DateTime: TDateTime; const InputIsUTC: Boolean; out Offset: Integer): Boolean;
+function GetLocalTimeOffset(const DateTime: TDateTime; const InputIsUTC: Boolean; out Offset: Integer; Out IsDST : boolean): Boolean;
 var
   Year: Integer;
 const
@@ -1053,12 +1053,16 @@ begin
       DSTStart := DSTStart + (TZInfo.Bias+TZInfo.StandardBias)/MinsPerDay;
       DSTEnd := DSTEnd + (TZInfo.Bias+TZInfo.DaylightBias)/MinsPerDay;
     end;
-    if (DSTStart<=DateTime) and (DateTime<DSTEnd) then
+    IsDST:=(DSTStart<=DateTime) and (DateTime<DSTEnd);
+    if isDst then
       Offset := TZInfo.Bias+TZInfo.DaylightBias
     else
       Offset := TZInfo.Bias+TZInfo.StandardBias;
   end else // no DST
+    begin
     Offset := TZInfo.Bias;
+    IsDST := False;
+    end;
   Result := True;
 end;