On two WP v2.0 blogs, I am using the "get_calendar()" template tag to display a monthly calendar on an archives list page (based off of the Default Theme's Archives page template). Typically, this calendar would always move on to the next month as soon as I created a post for the new month. I just made a post this morning at 1:01AM. So, typically, the calendar should have moved on to January 2006. Unfortunately, it is apparently stuck on December 2005.
In this forum thread, "Artemis" reported that the calendars on all of his blogs, three WP v1.5.2 blogs and one WP v2.0 blog, are stuck on December 2005. Artemis is also hearing similar reports of stuck calendars from a WordPress-related email group.