The Olympus PEN series seems to be afflicted with a malfunctioning (or incorrectly set up) capacitor. This capacitor holds enough power in the system to keep the settings, such as date and time, while the battery is being changed. Except that it isn’t working for me.
For me, upon taking out the battery out of my E-PL3, the date resets. Googling this issue I found this comment on Flicker:
Hi ransome2012 – just had the same problem and I solved it accidentally!
Try to remove the SD-card first and then change the battery. With my camera this saved date & time.
Greeting from Switzerland, Enzo
So the workaround is: Remove the SD Card before changing the battery!
With the SD card removed, the settings are persisted greater than 10mins.
My simple theory here is that the SD card (or a system that monitors the SD card) is being powered when the camera is off. That seems odd to me, but no doubt there is a reason. The result is too much power being used for the capacitor to handle. Perhaps, while being designed, the camera went through settings persistence testing with no SD card in place.
Still, the issue is ridiculous really.