I have a 2002 Impala. About 1 week ago this started. Every morning when I start my car the clock says 1200. No mater what time I start it. So I reset it to the right time which is about 6:30. As I go thru the day the time is correct. I get to work or run around and car is off for 1-6 hours during the day. I go to sleep, wake up, and wala it show 12:00. Keeps good time, but seems when it is off all night the clock will reset as if the battery was disconnected. this now happens every night. I wake up and have to reset the time. If I do not reset the time. After the start the car in the morning it will keep track of time. If I do not restet clock in morning the time will be wrong. Example: I start car at 6, but car says 12. I turn car off. and restart 3 hours later. Now car says 3:00 when it is 9:00. So after I start in morning it keeps good time and accurate. But after I go to sleep and restart in morning it starts at 12:00 or should I say resets itself to 12:00. So basically I have to reset the time every morning to have the correct time thruout the day. Help

 

Check battery cables and body grounds. Make sure they are clean and tight.