I couldn't say exactly when the problem with the date started happening, as it's a relatively new board and I don't pay much attention to what goes on at the bottom of the page.
However, I did have my board integrated with Photopost Pro, and had to remove a section of that particular hack this morning. It was the middle of the hack -- beginning and end portions stayed the same -- but somehow my date settings returned to normal. So, it must have been something in the body of the PP hack affecting the date, even though it wasn't anywhere near that section of ubb code.
Sorry for the fuss.