It seemed that the RTC battery in my new reform was dead (the time and date after start was always set to some time in December 22; the “hwclock -w” didn’t worked).
I didn’t find anywhere in docs (Operator Manual…, specs) what type of battery it is. It’s CR1220 (why so small one?).
So I replaced it and now I have correct time and can do “hwclock -w”!
it might be that 1220 is a standard size for laptops, frame.work also uses a 1220 (but theirs is ML, so rechargeable, which is an issue in and of itself)
I shorted something that drained my RTC battery a while back. Coin cell type is documented here, for future reference.
Thanks! For users like me it can be a bit hard to identify from this reference what is the battery type needed.