StartOfAYear ... StartOfTheYear ... EndOfAYear ... EndOfTheYear ... 每年、月、周、日的开始与结束的时间

{参数是指定的年、月、周、日}
DateUtils.StartOfAYear 
DateUtils.StartOfAMonth
DateUtils.StartOfAWeek 
DateUtils.StartOfADay

{参数是 TDateTime}
DateUtils.StartOfTheYear 
DateUtils.StartOfTheMonth
DateUtils.StartOfTheWeek 
DateUtils.StartOfTheDay

{参数是指定的年、月、周、日}
DateUtils.EndOfAYear 
DateUtils.EndOfAMonth
DateUtils.EndOfAWeek 
DateUtils.EndOfADay

{参数是 TDateTime}
DateUtils.EndOfTheYear
DateUtils.EndOfTheMonth
DateUtils.EndOfTheWeek
DateUtils.EndOfTheDay

unit Unit1;

interface

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

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

var
  Form1: TForm1;

implementation

{$R *.dfm}

uses DateUtils;

procedure TForm1.FormCreate(Sender: TObject);
var
  dt,t1,t2,t3,t4: TDateTime;
  s1,s2,s3,s4: string;
begin
  dt := StrToDateTime('2009-5-20 11:22:33');

  t1 := StartOfAYear(2009);
  t2 := StartOfTheYear(dt);
  t3 := EndOfAYear(2009);
  t4 := EndOfTheYear(dt);

  s1 := FormatDateTime('yyyy-m-d h:n:s:zzz', t1); //2009-1-1 0:0:0:000
  s2 := FormatDateTime('yyyy-m-d h:n:s:zzz', t2); //2009-1-1 0:0:0:000
  s3 := FormatDateTime('yyyy-m-d h:n:s:zzz', t3); //2009-12-31 23:59:59:999
  s4 := FormatDateTime('yyyy-m-d h:n:s:zzz', t4); //2009-12-31 23:59:59:999

  t1 := StartOfAMonth(2009, 5); { 2009 年 5 月 }
  t2 := StartOfTheMonth(dt);
  t3 := EndOfAMonth(2009, 5);
  t4 := EndOfTheMonth(dt);

  s1 := FormatDateTime('yyyy-m-d h:n:s:zzz', t1); //2009-5-1 0:0:0:000
  s2 := FormatDateTime('yyyy-m-d h:n:s:zzz', t2); //2009-5-1 0:0:0:000
  s3 := FormatDateTime('yyyy-m-d h:n:s:zzz', t3); //2009-5-31 23:59:59:999
  s4 := FormatDateTime('yyyy-m-d h:n:s:zzz', t4); //2009-5-31 23:59:59:999


  t1 := StartOfAWeek(2009, 21); { 2009 年第 21 周 }
  t2 := StartOfTheWeek(dt);
  t3 := EndOfAWeek(2009, 21);
  t4 := EndOfTheWeek(dt);

  s1 := FormatDateTime('yyyy-m-d h:n:s:zzz', t1); //2009-5-18 0:0:0:000
  s2 := FormatDateTime('yyyy-m-d h:n:s:zzz', t2); //2009-5-18 0:0:0:000
  s3 := FormatDateTime('yyyy-m-d h:n:s:zzz', t3); //2009-5-24 23:59:59:999
  s4 := FormatDateTime('yyyy-m-d h:n:s:zzz', t4); //2009-5-24 23:59:59:999

  t1 := StartOfADay(2009, 140); { 2009 年第 140 天 }
  t2 := StartOfTheDay(dt);
  t3 := EndOfADay(2009, 140);
  t4 := EndOfTheDay(dt);

  s1 := FormatDateTime('yyyy-m-d h:n:s:zzz', t1); //2009-5-20 0:0:0:000
  s2 := FormatDateTime('yyyy-m-d h:n:s:zzz', t2); //2009-5-20 0:0:0:000
  s3 := FormatDateTime('yyyy-m-d h:n:s:zzz', t3); //2009-5-20 23:59:59:999
  s4 := FormatDateTime('yyyy-m-d h:n:s:zzz', t4); //2009-5-20 23:59:59:999
end;

end.

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DateUtils-Function

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