I recently installed a new radio in my old car. I'm not really sure whats happening but every once in a while the date and my saved radio stations will disappear and i have to reset them. The weird part is that all my other settings, color of text, sub woofer level etc will stay the same. The name is Kenwood Excelon DPX792BH.
Car radios usually have two power inputs - one connected directly to the battery (thru a fuse, of course), the other one connected to ACC/ON circuit in the car. Make sure that direct connection is OK, and you did not have replaced your car' battery.