GetTimeZoneInformation() enables you to get timezone information in standard name, standard bias, daylight name, and daylight bias.

Below code shows the current timezone in the local machine:

uses System.DateUtils;

.
.
.

procedure TMainFrm.GetTimezone;
var
  s: String;
  ZoneInfo: TTimeZoneInformation;
begin
  GetTimeZoneInformation(ZoneInfo);
  s := 'Bias: ' + IntToStr(ZoneInfo.Bias);
  s := s + #13 + #10 + 'StandardName: ' + ZoneInfo.StandardName;
  s := s + #13 + #10 + 'StandardBias: ' + IntToStr(ZoneInfo.StandardBias);
  s := s + #13 + #10 + 'DaylightName: ' + ZoneInfo.DaylightName;
  s := s + #13 + #10 + 'DaylightBias: ' + IntToStr(ZoneInfo.DaylightBias);
end;

You will see the result like below: