Windows clock problem
When this happens, in general it is because the computer's real time clock battery (also known as RTC battery, CMOS battery or BIOS battery) is depleted. It is not the power battery at the back of your device - generally it is located inside the PC and looks like a small coin with the size of a dime or a quarter. If you search in image.google.com for CR2032 or CR2016 you will see different brands and assemblies for them.
It is the power of this battery that is used to maintain the real time clock circuit working when you switch off or remove the power or the main battery from your PC, keeping the date and time being updated continuously.
To change it, you will need to unscrew and remove the back covers of your device and look for this kind of battery. Buy another one with the same size and thickness (check their model, like the ones mentioned above) and reinsert it to the same holder where you took it from. If it is soldered to a cable and connector, you will need to find one assembled like that or you will have to ask a repair technician to do unsolder the cable from the oldest one and solder it to the new one for you (always remembering to isolate it with electrical tape before connecting it to the circuit, to avoid short circuits).
In the next time you power your device on, it may warn you that the CMOS battery was changed and you will have to enter the BIOS setup and adjust it accordingly. The next time you switch it off and on again, it is supposed to work properly, without resetting the date and time.
Hope you may find this helpful!
Miguel Luiz Martins
CTL 2goPC Tablet
on Nov 20, 2013