IsLeapYear、IsInLeapYear - 是否是闰年
SysUtils.IsLeapYear();
DateUtils.IsInLeapYear();
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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
b: Boolean;
begin
b := IsLeapYear(2009); //False
b := IsLeapYear(2012); //True

b := IsInLeapYear(StrToDateTime('2009-1-1')); //False
b := IsInLeapYear(StrToDateTime('2012-1-1')); //True

// ShowMessage(BoolToStr(b, True));
end;

end.