Printer forgets date & time after powering down

[Matt-Mfd283]

My LaserJet Pro MFP M283fdw does not retain the time and date since approx the summer. I’ve owned the printer for a number of years and this is a new problem. Whenever I switch it on, it has defaulted to 01Jan2000, 00:00. I have set date & time  many times manually using the printer touchscreen, but it always defaults to January 01, 2000 after a power down.

It is constantly connected to mains power and connected to the network. We have power shortages about once a year, but this happens after every switch off from manually pressing the power button or switching off as a result of power save settings. My usage pattern has not changed and apart from applying firmware updates I have not done any software or settings changes. It sits there and simply prints and scans. No need to make any changes, as it works. Also the wall socket has not changed either, the power cable has been checked repeatedly. But all scans now show wrong date and time stamps, unless I enter the correct date and time manually after switching on. 

Questions:

is there a battery somewhere that needs to be replaced?

or has a recent firmware update created this memory loss?

Would appreciate someone who can provide a response to how to address this recently recurring  issue. 

[Repairatrooper]

if there is a backup battery (usually a coin cell), in my experience it will likely be soldered to the main board and not a quick replacement. 

[Matt-Mfd283]

Thanks, that question is as so often, the pivotal one, before one can spring into action: is it hardware (e.g. a battery soldered on) or is it software?

anyone in the know, please? 
thanks!