function AdjustedTimeZoneBias: Integer;
var
  TZI: Windows.TTimeZoneInformation;  // info about time zone
begin
  Result := 0;  // keeps compiler quiet
  case Windows.GetTimeZoneInformation(TZI) of
    Windows.TIME_ZONE_ID_INVALID: SysUtils.RaiseLastOSError;
    Windows.TIME_ZONE_ID_STANDARD: Result := TZI.Bias + TZI.StandardBias;
    Windows.TIME_ZONE_ID_DAYLIGHT: Result := TZI.Bias + TZI.DaylightBias;
    Windows.TIME_ZONE_ID_UNKNOWN: Result := TZI.Bias;
  end;
end;
//delphi/2158