My watch is model # DW-5600BB. This morning, I noticed it was reset to Jan 1st 2010 and the display read 12:38 when I looked at it. I assume it was reset to 12:00, and I noticed later on.
Sometimes, I notice the display on the watch starts to get dim and then it comes back up. For example, when I set the correct time today, the display was dimming out but when I pressed a button to make an adjustment, it looked fine. Also, sometimes the fading happens randomly, seems to weaken a little and then come back strong.
I suppose the obvious thing is the battery, but I've only had the watch for about a year and purchased it new. Maybe it was sitting on the shelf a few years, hence the 2010 reset date? How long would the battery typically last? This model in particular has a blacked out display, I guess you could call it a reverse LCD? Does this 'reverse' LCD consume battery faster?
I also rarely use any other features of the watch, hardly ever use the backlight, alarm, or stop watches. I'll just set the time every few months, it only differs by a few seconds, keeps good time.