Chosen Solution

The internal data battery does not hold the date and time when replacing the main battery on my Olympus E-PL1. What type of battery is it? and where is it located? I hope you can help

It’s likely that the camera uses a capacitor to keep the clock and memory up while changing the main battery. If the cap fails (as they sometime do) then you’ll see this problem. If that’s the case the only solution is having it repaired. I found this during a search. https://www.dpreview.com/forums/thread/3