jquery - jQuery: Set cookie time to unimited

Question

I am using following code bt its not wokring:-

var newdate = date.setTime(date.getTime() + (60 * 60 * 24 * 30)); //expire after 30 days
$.jqx.cookie.cookie('cookieName', true, { expires: newdate}); 

I am using jQWidget to set the cookie.