Okay.
For the past, like, year or so, my computer's clock had been randomly resetting itself an hour back. It'd happen while the computer was running at totally arbitrary times during the day.
My first assumption was that the BIOS's little battery had been lightly toasted by one power surge or another, and therefore periodically fucked up what time it was. This was something I figured I couldn't fix, so I let it be.
I recall investigating the "Automatically adjust for daylight savings" setting and being sure that it is unchecked; it is. I also made positive that my time zone setting is correct (Eastern Time), and it is.
Then, today, for the very first time, I noticed this little tab right here:
As an experiment, I made sure the time was set correctly on the computer (3:24 PM), then I hit the Update Now button. Sure enough, the computer's clock jumped an hour backward, to 2:24 PM.
Every week, the time was being "resynchronized." To an incorrect time.