Duh, I'm a bonehead. Actually, I was using lowercase n, which shows the month number (as in 1-12) not the day of the month. Just didn't read carefully. I love it when fixes are so simple, and hate it when I do stuff like this.

Thanks.

M n, Y

I was adjusting the date format in the options admin screen today, and after one change I noticed that all the last post dates were wrong (notice that some posts were made in the future, ala "Today at 11:23pm") and many - not all - "user registered" dates were reset to Jan 1, 2006, which is a couple weeks before the launch of this forum.
You can see this here:

http://organanddrums.net/forum/userlist.php

I never entered an incorrect date format (I am experienced in PHP) that might have thrown something off. The only thing that I can think that I did differently was that I hit "return" when changing the date display once instead of clicking the "Save changes" button.

Any help on how to fix this or why this happened?