Computer Shows Wrong Date And Time

Older computers may keep losing the correct date and time after being switched off – fixing it is easy. In our computer repair business we come across this issue quite often with older computer – they keep losing the time, often changing to a date from many years ago.

Another sign of this problem is a warning message as soon as you turn on the computer about CMOS e.g. ‘CMOS checksum failure’.

Why Do The Date and Time Go Wrong? In very simple terms, computers have a digital (system) clock stored in the motherboard – the main system board inside the computer. This clock is kept powered on by a small battery like the one shown – when the computer is switched off, the battery enables the system clock to maintain the correct date and time – just like a digital watch.

Other configuration settings (CMOS) of the computer are also kept stored by the power from this battery. When Windows starts up it gets the date and time from the system clock inside the computer – so if the system clock is wrong, the date and time in Windows will also be wrong.

After a few years the battery dies so when the computer is switched off the system clock loses the correct date/time. When it is switched back on it uses the original date and time that the motherboard was manufactured, possibly many years ago. Stored CMOS settings are also lost – hence the warnings about CMOS at startup.

How To Fix It – You need to replace the battery with a new one and set the correct date and time in the computer BIOS (and any custom settings). The new battery will then keep this clock accurate and Windows should automatically get the right date/time from it.

Warning: if you have a laptop, we advise taking it to a computer repair specialist as it may be necessary to remove the keyboard or take the whole laptop apart to access and replace the old battery – which may also not be a standard type…

With a PC, things are easier and you should be able to do it yourself.

CR2032 battery
Typical CR2032 BIOS battery

How To Replace The Battery – If you are not confident working inside your computer then take it to a computer repair specialist.

  1. Make sure your computer is switched off and all leads are disconnected.
  2. Discharge any static electricity on you by touching the bare metal of a radiator or pipe leading to ground.
  3. Open your computer case – usually by removing one side panel.
  4. Locate the battery inside – it is usually a round flat CR2032 battery like the one shown above (if you cannot see it or yours is different contact a PC repair specialist for advice).
  5. Remove the old battery – most have a small clip holding the battery in place in which case you need to move the clip slightly to pull the battery out.
  6. Now fit the new battery. You usually just push it into place but make sure you insert it in the same way as the old one i.e. the + sign and writing on the battery should face the same direction as the old one.
  7. Close the case (e.g. refit the side panel) and switch on the PC.
  8. Enter the PC’s BIOS Setup utility and input the correct date and time.You can find instructions in our article here on how to enter the BIOS, find your way around and save any changes.

After saving your changes and exiting the BIOS your PC should restart and maintain the correct settings, date and time :-)