When I wake up my MacBook Air (early 2014), the system date falls back to December 31, 2019. macOS Catalina 10.15.7 (19H2).
My first suggestion is that the CMOS battery is dead. I don’t know enough about Macs to know if they even have a CMOS battery, but on PCs that is where the date is stored. A Google for the topic says that Mac Mini’s have one, though they seem to call it a PRAM (Parameter RAM) battery. https://www.youtube.com/watch?v=Y56eHhFrhZ8 I don’t suspect you could fix this yourself on a MacBook Air, so I think you’re going to need to involve Apple Support.
Yeah, it sounds like the PRAM battery, you could try a PRAM reset and that might help but most likely you will need to get the PRAM battery replaced.
PRAM reset is done when booting the mac you hold down:
So far, the system date is holding after doing the PRAM reset. I also did the SMC reset. Thank you James.
It appears MacBooks (including Air) do not have a CMOS or PRAM battery. They use a capacitor powered off the lithium ion battery. May be one of the reasons they power down before the battery is fully discharged.
The 31 Dec 2019 date was suspicious. Would expect an epoch date if PRAM lost power.
Found this article interesting in terms of MacBook sleep settings. Something for me to look at in the morning on my MBA.
No problem I’m glad it possibly helped.