procedure TForm1.button1Click(Sender: TObject);
var
y: integer;
begin
y := StrToInt(edit1.Text);
if (y mod 4 = 0) and (y mod 100 <> 0) or (y mod 400 = 0) then
label1.Caption := edit1.Text + '是闰年'
else
label1.Caption := edit1.Text + '不是闰年';
end;