Open the chassis and see the motherboard. There is usually a coin-shaped button next to it, which can be pulled out by pressing it. You can buy a new battery and replace it in a computer shop or a watch shop. Usually only a few dollars. If the motherboard battery is dead, the time will be out of sync after the computer is turned on, unless your computer is turned off. If you turn off the power and play for a few hours, the time will return to the initial state. There is no big impact in other places. good luck