Delphi – Gets TTIMEZONE in a non-local time zone and converts between time zones

uses
 ..., TZDB;

procedure Main;
var
 ServerTZID: string;
 TZ: TTimeZone;
 Stamp1, Stamp2: TDateTime;
begin
 // 1. retrieve server timezone info
 ServerTZID := ... // MyServer.GetTimezoneInfo; eg ' Pacific Standard Time';
 // look up the retrieved timezone
 TZ := TBundledTimeZone.GetTimeZone(ServerTZID); // nil if not found
 // 2. retrieve server timestamp
 Stamp1 := ... // MyServer.RetrieveTimestamp;
 // 3. convert to UTC and back to local timezone
 Stamp2 := TZ.Local.ToLocalTime(TZ.ToUniversalTime(Stamp1)); 

 Writeln(Format('%s %s -> %s %s', [FormatDateTime('yyyy-mm-dd hh:n n:ss.zzz', Stamp1),
 TZ.DisplayName, FormatDateTime('yyyy-mm-dd hh:nn:ss.zzz', Stamp2),
 TZ.Local.DisplayName])) ;
end;

See answer in English> How to convert a historical timestamp to a different time zone with DST in Delphi? 1 my topic It may be very worded, but this is what I have.

I have a web service that reports a timestamp in local time, and if the server is in the affected area, the timestamp reflects daylight time The web service also has a second call to retrieve the server time in UTC, so the server in Pacific Daylight Time (PDT) reports its UTC offset as -08:00, even though it is actually -07 due to PDT: 00.

This is the result of my call to return the server time zone information.

Pacific Standard Time; -480; (UTC-08: 00) Pacific Time (US and Canada); Pacific Standard time; Pacific Daylight Time; [01: 01: 0001; 12: 31: 2006; 60; [0; 02] :0: 00; 4; 1; 0;]; [0; 02: 00: 00; 10 ; 5; 0;];] [01: 01: 2007; 12: 31: 9999; 60; [0; 02: 00: 00; 3; 2; 0;]; [0; 02: 00: 00; 11 ; 1; 0;];];

So if the timestamp returned from the web service is 3/12/2013 12:00 am and the UTC offset is -08:00 and I live in Arizona The state’s daytime time exempt area, my UTC offset is -07:00. How can I convert the returned timestamp to local time?

The killer here is web services that use local timestamps. If they just stick to a common format, my life will be easier. My current thinking is if I can use TTimeZone or equivalent structure To get the server information, then I can use the TTimeZone.IsDaylightTime(Timestamp) function to know if I need to subtract an hour offset and -07:00 local offset from the timestamp before using the -08:00 server. The correct local time.

You can use delphi-tzdb. Pseudo code:

 uses
 ..., TZDB;

procedure Main;
var
 ServerTZID: string;
 TZ: TTimeZone;
 Stamp1, Stamp2 : TDateTime;
begin
 // 1. retrieve server timezone info
 ServerTZID := ... // MyServer.GetTimezoneInfo; eg'Pacific Standard Time';
 // look up the retrieved timezone
 TZ := TBundledTimeZone.GetTimeZone(ServerTZID); // nil if not found
 // 2. retrieve server timestamp
 Stamp1 := ... // MyServer.RetrieveTimestamp ;
 // 3. convert to UTC and back to local timezone
 Stamp2 := TZ.Local.ToLocalTime(TZ.ToUniversalTime(Stamp1));

 Writeln(Format( '%s %s -> %s %s', [FormatDateTime('yyyy-mm-dd hh:nn:ss.zzz', Stamp1),
 TZ.DisplayName, FormatDate Time('yyyy-mm-dd hh:nn:ss.zzz', Stamp2),
 TZ.Local.DisplayName]));
end;