Node doesn't expire

I've installed this module and used the admin settings to expire my CCK content type after 30 days. I then edit the authoring date of an existing CCK node to 1 year ago. Then I run chron. The node isn't expired and when I click on the extend link it gives this message:

<<Name of node>> will expire on 1 January 1970 - 1:00am
that is in 0 sec.

You can extend it with 30 days.

Where <> is the actual title of the node. Am I testing it the right way, or should I wait 30 days to see if it works? ;)