Some calendars not posting free/busy infor past 6 months   

I have some resource mailboxes that are not posting their free/busy infor 
past 6 months in their calendars.
If I go into the mailbox for these resources, I see that it says publish 12 
months every 15 minutes.
Any ideas?

date: Mon, 21 Mar 2005 07:15:03 -0800   author:   Jason Loster