var t, t1, t2: TDateTime;
   hh, nn, ss, ms: Word;
begin
  t1 := StrToTime('20:20:20');
  t2 := StrToTime('22:50:30');
  t := t2 - t1;
  DecodeTime(t, hh, nn, ss, ms);
  ShowMessage('時間差距 '   IntToStr(hh)   ' 時 ' 
      IntToStr(nn)   ' 分 '   IntToStr(ss)   ' 秒';
end;