Clock won't keep time when car is off for a day
 

the battery is new and there is no corrosion or anything on the terminals.... when the car sits for over a day (car/ignition off, parked..) the clock loses the time setting sometimes... everything else in the car works fine and the head unit also has time and it doesn't lose time or the presets so I don't think its something w/ power delivery/battery... other than checking the wiring is there anything else to look for on the stock clock? or do you think its messed up somehow?

w/ the motor running.. if you set the time.. it will be accurate the whole time its running... and if you use the car not too long after.. but if you let it sit for a day the time setting resets/time is incorrect.. what could it be? thanks in advance for your input...