If your computer is losing date and time after it’s powered off, the most likely cause is the CMOS battery failing.

This can also be followed by errors on bootup such as CMOS checksum error which confirms an issue with the battery.

The CMOS battery is very small usually a coin size type. It is used to store all setting information including the date and time.

When the battery is exhausted all settings information will be lost each time the computer is powered off and unplugged from the mains.

If the computer has not been used for a few months, powering it on and leaving it on for a period of around 24 hours may fix this.

Otherwise the CMOS battery will need to be replaced.

In desktop computers the CMOS battery is usually very easy to find and replace, but laptops can be a specialised job as it can be very difficult to find let alone access and replace.

Once you’ve located the battery obtain all of the information written on it, if possible remove it and take it with you when purchasing a replacement to ensure compatibility.

If ordering online you may only need to specify your computer make and model to find the correct battery.

When attempting to remove the battery make sure you are well earthed to reduce the chance of ESD or Electro Static Discharge which can easily damage electronic components, such as motherboards.

To remove the battery, unclip or gently prise it free, it should then life or flip out.

On older generation computers the battery may be very similar to an older type camera battery, it also worth noting some manufacturers soldered the batteries in place, so you may need to find someone who is handy with a soldering iron to replace this type.

When fitting the new battery you’ll need to setup the CMOS settings one more time.

CMOS batteries are usually expected to last around 5 years, but they usually last longer depending on how the computer is used and if it is left plugged into the electrical mains supply.

If replacing the battery does not stop your computer from losing date and time check to make sure the connections from the motherboard to the battery are not tarnished. If it is still losing CMOS settings after checking this, the issue may be a problem with the motherboard itself.

Motherboard hardware problems are generally not cost efficient to repair, so replacing is usually the best way to resolve this.

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