I'm a little rusty, but I'm going to work on an a mod for attachment.php

I want to compare today's date to the date that each member registered on the forum and do something different if they have been a member for more than 30 days.
In
attachment.php, does the
$vbulletin->userinfo array contain the member's join/registration date? If so, how can I access this variable to compare it to today's date?
Thanks for your help,
James