TOPIC: Funny Error with repeats

Here's an odd problem - maybe someone has an idea about it?

I created an event that repeats on Thursdays in the first week of each month for about 100 months (some long time - it's a monthly meeting).

It went off and created the event and all looks ok, but when I was scrolling through the months, I noticed that November 2013's meeting is on a Wednesday. October is right, December is right (as are the other 2013 months).

Any ideas what I might look for? I've created a trouble ticket but haven't had any activity on that (it's been around a week)