sudo LC_ALL=C /sbin/tune2fs -l /dev/nvme0n1 |grep 2022
tune2fs 1.46.6-rc1 (12-Sep-2022)
Last mount time: Thu Dec 29 20:05:22 2022
Last write time: Fri Dec 30 11:14:35 2022
Last checked: Wed Aug 31 09:37:57 2022
(It looks like "Last write time" is actually "Last umount time", because it is not refreshed during usage of the FS)
This is handled for example by fake-hwclock package in Debian (also RaspberryPi OS, installed by default) - it saves it in file, and even updates it every hour (so you won't teleport more than a hour back in time after unclean reboot). However, it of course does not work when you mount read-only because you don't want your microSD card to fail.
Interesting! Unfortunately due to write endurance many networking devices mount their filesystem read-only. This means they also sometimes lack a log file describing why the device shut down!
