Try setting the system time in the BIOS. It's possible that It's unable to save the time due to a problem with the system clock.
When you first turn on your computer there should be a message saying something like "press F2 for setup" Press it quickly.
Every bios is a bit different, but if you navigate you should see a time setting. Set it to the correct time and see what happens.
If it still does not set correctly you could have a dead or incorrectly inserted battery.