[stumped]

cause ?
this is the device my son has on extended loan. he'd been moaning that recently added books were not there , which I was sure I'd sideloaded

so we check it out
I connect to calibre - check the on device column & add a few more - looks fine to me - and also see that some of the allegedly missing titles were on device.

disconnect it, hand it back...
he takes it - flips the sort order to" recently added" & says look : nothing new there... sure enough - page 1 of recently added looks well out of date. I sort by author & find the new ones Ok that way...

OK - so I flip it to settings... date and time and see 2012 ! which does explain the issue and means he can't trust that date added unless we delete & reload stuff

my question is how did it get like that.

I know we keep it offline so it does not get an internet time check, and clearly connecting to calibre does not force a date and time correction, but do Kobo readers also forget what year it is if battery goes flat ?
or must it have been a fat finger episode ?

I am sure it has been online more recently than 2012 as I reckon I did a firmware update check a couple of years ago
and my PC, which is online, does know that its 5th december 2019