unit Unit1;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs,DateUtils, StdCtrls, Math;

type
  TForm1 = class(TForm)
    btn1: TButton;
    procedure btn1Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

procedure TForm1.btn1Click(Sender: TObject);
var
  ZoneInfo: TTimeZoneInformation;
  st: _SYSTEMTIME;
  Bias: Integer;
  tmp : TDateTime;
  znk: Char;
begin
  case GetTimeZoneInformation(ZoneInfo) of
        TIME_ZONE_ID_STANDARD:
            Bias := ZoneInfo.Bias + ZoneInfo.StandardBias;
        TIME_ZONE_ID_DAYLIGHT:
            Bias := ZoneInfo.Bias + ZoneInfo.DaylightBias;
        TIME_ZONE_ID_UNKNOWN:
            Bias := ZoneInfo.Bias;
        else
            Bias := 180;
    end;
  znk:='+';  
  if Bias<0 then znk:='-';
  ShowMessage(FormatDateTime('yyyy-mm-dd',now)+'T'+FormatDateTime('hh:nn:ss',now)+znk+FormatFloat('00',Abs(Bias) div 60)+':'+FormatFloat('00',Abs(Bias) mod 60));


end;

end.

  if Bias>=0 then znk:='-';