You may have gathered by now that a major use of the TikiWiki on my site (www.progressiveomaha.com/tikidir) is to post calendar events. I hope the notices I've put here end up in the Bug Report section. If they don't, let me know and I'll track down how to do that again.
Meanwhile: I've tried posting an entry in the calendar for the date January 31, 2009. Nothing displays. I've tried posting it using "Save", "Duplicate" and also by viewing the "Preview" and trying to "Save" from there. The entry just disappears. So far I've not had this problem with any other date.
Actually, I just tried March 31, and a test entry worked there; so it's not the date.
Another candidate for the bug report.