setcookie(), logout

I'm going over some code handed to me, a logout function: function user_logout() { setcookie( 'user_name', '',(time()+28800), '/', '',0); setcookie( 'id_hash', '',(time()+28800), '/', '',0); } Doesn't this mean the cookie will expire after 8 hrs? So what's this really doing? Moreover I found this contrib. note on the setcookie reference pg.: Then why have I not seen anybody using the client's time? Note: Just as a note, You might want to use the client browers time to set your expires, using your local time might mean your cookie wont expire for 24 hours. -Pushkar S. Pradhan