CakePHP: question about Cookies expire

if 1 cookie is create by $this->Cookie->write('Rating', $cookie, true, '+1 months'); after 15 day, I read :

 $this->Cookie->read('Rating');
    do somthing .... this   
$this->开发者_StackOverflowCookie->write('Rating', $cookie, true, '+1 months');

Then now expire of rating cookies is 15 days or 1 month ?

It should still be 1 month.