Running an Ion XE and every time the console is powered up from being in storage the date and time are incorrect. After fixing in the settings it will hold as long as the mains power is not disconnected. Disconnect it and reboot, date and time reverts to 12:00am January 1st, 2012 (or something like that I don't have the console in front of me ATM).
I would guess that this is probably a battery issue. #1 - Am I correct? #2 - Is this something I can service myself? #3 - If so, is there any documentation that would guide me through the process?
I think this is the mainboard battery. Call the Tech Service for further steps.
sstaub is exactly right, this sounds like the BIOS CMOS battery. Check out this Support Article: What Happens When I Remove the BIOS Battery in an Ion Xe? - Electronic Theatre Controls Inc
Here are the instructions to open an Ion XE or XE 20: How to Open Ion Xe or Ion Xe 20 - Electronic Theatre Controls Inc