Xbox 360 date/time keeps resetting

[Teaf]

My date/time on my Xbox 360 constantly resets to defaults when the machine has been off for a few hours. Is it because I don't have a hard drive or something or do these use a 2032 battery like pc motherboards do and it may be dead? Or something else?

Suggestions / help appreciated

 

[Teaf]

When it's off I tend to turn it off at the mains rather than just the console itself, so I guess this could be why. Gonna have to shift plugs around I think to keep it turned on at the mains and see if that helps. I'm not connected to Live either, since I don't use it. Cheers folks!