var i, iWeek: integer;
  dt: TDateTime;
begin
  for i := 1 to 12 do begin
    dt := EncodeDate(2003, i, 1); // 先求出每月 1 日的值
    iWeek := DayOfWeek(dt); // 再判斷每月 1 日是星期幾
    case iWeek of // 依每月 1 日是星期幾的值, 再加幾為星期三
      1: dt := dt   3; // Sunday
      2: dt := dt   2; // Monday
      3: dt := dt   1; // Tuesday
      5: dt := dt   6; // Thursday
      6: dt := dt   5; // Friday
      7: dt := dt   4; // Saturday
    end;
    ListBox1.Items.Add(FormatDateTime('YYYY/MM/DD', dt));
  end;
end;