It’s a good read, and I really wish time was always that simple. Sometimes you have multiple platforms on different clock systems and distributed systems running across them. Did you know google and amazon smear leap seconds? GPS/Galileo/that-China-one don’t have leap seconds (but all are different TAI offsets) but that Russian GPS one does have leaps. They all have slightly different versions of utc.

Most of the time none of that matters and you can just install chronie and point it to whatever.pool.ntp.org and you’re off to the races. But boy does it suck when you have to to know.