Code:

...
function RunControlPanelApplet(sAppletFileName: string): Integer;
begin
  Result := WinExec(PChar('rundll32.exe shell32.dll,' +
                    'Control_RunDLL ' + sAppletFileName),
                    SW_SHOWNORMAL);
end;
...
//Za Regional settings:

procedure TForm1.Button1Click(Sender: TObject);
begin
  RunControlPanelApplet('Intl.cpl');
end;

//Za Date/Time:

procedure TForm1.Button2Click(Sender: TObject);
begin
  RunControlPanelApplet('timedate.cpl');
end;