Reset the CMOS. Unplug your computer from network and power, remove the button cell battery and clear the CMOS. There should be a CLR_CMOS jumper that needs to be moved over 2 pins. There are plenty of tutorials on how to clear cmos around here. Sorry I can't be more precise. Also, if that doesn't solve your problem, change the "Time update server" in windows. There are many servers available, again, google up how to do that too.