function TimeZoneName: string;
var
  TZI: Windows.TTimeZoneInformation;  // info about time zone
begin
  case GetTimeZoneInformation(TZI) of
    Windows.TIME_ZONE_ID_INVALID: SysUtils.RaiseLastOSError;
    Windows.TIME_ZONE_ID_STANDARD: Result := TZI.StandardName;
    Windows.TIME_ZONE_ID_DAYLIGHT: Result := TZI.DaylightName;
    Windows.TIME_ZONE_ID_UNKNOWN: Result := '';
  end;
end;
//delphi/2188