Electrical, clock needs resetting after key is turned off
 

08 Silverado 1500. After I turn off the truck and then turn it back on the clock on the dash/radio goes to 1200. Is it a problem with the ignition or the radio?

More than likely a blown fuse. Check them all.

if its an aftermarket radio...its been wired up wrong.

Thank you, I will check the fuses.I may have left out an important piece of information. It is intermitent. It also seems to occur more if is sits unused for a few days. But it will occasionally occur several times a day.

Thank you for the reply, but it is original.

the radio will have a switched power feed and a constant power feed. if it loses the constant power feed or its grd the radio time will reset. there are multiple radio builds so it hard to give specific information without knowing the radio build code.

the radio may have more than one fuse.
the radio itself may be bad.

Thanks again, it may be a bad radio, because sometimes both door speakers go out for several days then they just start working again.