Originally Posted by pete.i
A failing or failed bios battery can also cause this. I have had the clock change to random times when the battery is on it's way out and a failed battery will cause the clock to reset to 00.00 midnight.
Itís a round silver coin lithium battery very small and you have to open case to replace it. If clock changes without connecting to internet then take Pete suggestion.
Also you can try changing time in BIOS settings once replaced.