1. Your CMOS battery could be dead/dying. If that is the case, you would need to replace it.
2. Your time zone could be set incorrectly on the device causing it to not register changes correctly. You would then need to correct the time zone on the computer to fix it.
3. You have a virus or malware on the device that is causing the problem. In this case you would need to do run a few programs to check for viruses and malware to make sure there isn't any and if there is to clean it up.