systemd does something of late where it will try to put the clock back to somewhere closer to “now” when it detects a value that’s too far in the past. I suspect it just digs around in the journal, grabs the last timestamp from that, and runs with it. This is usually pretty good, since if you’re just doing a commanded reboot, the difference is a few seconds, and your time sync stuff fixes the rest not long thereafter.
Ooh, that’s a great set of interlocking problems. Time is one of those things that so often works perfectly, until it doesn’t.
It’s actually
/var/lib/systemd/timesync/clock.This is a classic issue I’ve run into myself. It should be solved in v248, but I haven’t tested that personally.