CompareDateTime、CompareDate、CompareTime、SameDateTime、SameDate、SameTime - 对比时间的函数

CompareDateTime、CompareDate、CompareTime 返回的是 -1、0、1;
前者 = 后者: 返回 0;
前者 > 后者: 返回 1;
前者 < 后者: 返回 -1;

SameDateTime、SameDate、SameTime 返回的是 True 和 False.

unit Unit1;

interface

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

type
  TForm1 = class(TForm)
    procedure FormCreate(Sender: TObject);
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

uses DateUtils;

procedure TForm1.FormCreate(Sender: TObject);
var
  t1,t2: TDateTime;
  r1,r2,r3: Integer;
  b1,b2,b3: Boolean;
begin
  {日期一致、时间不一致}
  t1 := StrToDateTime('2009-5-20 1:1:1');
  t2 := StrToDateTime('2009-5-20 1:0:0');

  r1 := CompareDateTime(t1, t2); //1
  r2 := CompareDate(t1, t2);     //0
  r3 := CompareTime(t1, t2);     //1

  b1 := SameDateTime(t1, t2);    //False
  b2 := SameDate(t1, t2);        //True
  b3 := SameTime(t1, t2);        //False

  {日期不一致、时间一致}
  t1 := StrToDateTime('2009-5-20 1:1:1');
  t2 := StrToDateTime('2009-5-21 1:1:1');

  r1 := CompareDateTime(t1, t2); //-1
  r2 := CompareDate(t1, t2);     //-1
  r3 := CompareTime(t1, t2);     //0

  b1 := SameDateTime(t1, t2);    //False
  b2 := SameDate(t1, t2);        //False
  b3 := SameTime(t1, t2);        //True

  {日期、时间都不一致}
  t1 := StrToDateTime('2009-5-19 1:1:1');
  t2 := StrToDateTime('2009-5-20 0:0:0');

  r1 := CompareDateTime(t1, t2); //-1
  r2 := CompareDate(t1, t2);     //-1
  r3 := CompareTime(t1, t2);     //1

  b1 := SameDateTime(t1, t2);    //False
  b2 := SameDate(t1, t2);        //False
  b3 := SameTime(t1, t2);        //False
end;

end.

DateUtils-Function