procedure TForm1.Button1Click(Sender: TObject);
var
  date1, date2: TDateTime;
  difference: Integer;
begin
  date1 := EncodeDate(2006, 01, 15);
  date2 := EncodeDate(2000, 01, 01);
  difference := trunc(date1) - trunc(date2);
  ShowMessage(IntToStr(difference));
end;