Delphi中对比时间：CompareDateTime、CompareDate、CompareTime函数

Delphi中对比时间：CompareDateTime、CompareDate、CompareTime函数2012-01-30 博客园万一CompareDateTime、CompareDate、CompareTime 都是对比时间的函数;

CompareDate 只对比日期部分, CompareTime 之对比时间部分.

两个参数都是 TDateTime 类型, 如果:

前者 = 后者: 返回 0;

前者 > 后者: 返回 1;

前者 < 后者: 返回 -1;

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;
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
 ShowMessageFmt（"%d,%d,%d", [r1,r2,r3]）; //1,0,1

 {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
 ShowMessageFmt（"%d,%d,%d", [r1,r2,r3]）; //1,0,1

 {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
 ShowMessageFmt（"%d,%d,%d", [r1,r2,r3]）; //1,0,1
end;

end.