In the episode, Joe asks Dave and Lisa, jokingly, ask if they got drunk and made out at the Christmas party. Later, Joe asks Matthew why he cares so much about Catherine's birthday. He said because his birthday was a week earlier and everyone forgot. However, in another episode, Matthew says his birthday is 12/21/65 (Andy Dick's real birthday). So I thought maybe this episode was out of order. Maybe it should go AFTER the Christmas episode. Except for one thing. In the beginning, Bill says, on the radio, that it's November. I know it's a sitcom and continuity errors seem to be a must. But it's always bothered me.

What do you think about it?

I would chalk it up to a simple continuity error by the writers. They probably don't consider things like characters birthdays a major plot issue, and it is easy to see how such an inconsistency could have been overlooked as the series progressed.