Javascript cookies clear the next day

Hi, we're trying to set a cookie using javascript that doesn't expiry for at least 6 month.

We're using this function to set a cookie

function setCookie(name, value, seconds) {
 
      if (typeof(seconds) != 'undefined') {
            var date = new Date();
            date.setTime(date.getTime() + (seconds*1000));
            var expires = "; expires=" + date.toGMTString();
            } else {
            var expires = "";
            }
 
      document.cookie = name+"="+value+expires+"; path=/";
      }

and then this to initiate the cookie...
setCookie('resources_user_id',response,15778463);

The cookie seems to work ok until the next day when you log into the site and the cookie has been cleared.

Am I doing something wrong?