There's a small battery on the logic board, which one and only assignment is to save date and time. If you noticing your keybox SC losing date even after you just re-set it, the battery most likely died.
The action is to simply change the battery, we use Varta CR1216 Lithium 3V Battery 25 mAh but any brand will do as long as it is the same model type.
To remove the battery you should cut the power, then use a plastic tool and gently work from the left to the right until the battery is out of the pocket. (see image)
