I think the calendar for this version of the vBulletin forum was only good until Dec 2006. I vaguely recall trying a few years ago to enter something for 2007 and discovering the calendar stopped at 2006.
(probably their way of ensuring that you keep upgrading)

hmm... so does this mean we don't get to celebrate LatsDay or
SchmangeDay until we upgrade the forum again?

I demand my beer and hookers dammit!