Blast from the past

I was surprised to find my less-than-a-year-old HP Microserver Gen8 taking over half an hour to come back from each reboot. Closer inspection showed the system clock jumping back to 2016 every time it restarted, which forces an fsck when Linux realises its disks have been modified "in the future". Checking >1TB of disk takes a long time.

It's been a while since I had to replace a CMOS battery, but it fixed the problem: