Hacker news discussion: https://news.ycombinator.com/item?id=44370426

There are different measure of time. Civil time is used in our contemporary society because talking in epoch (seconds since 1st Jananuary 1970) because it's too complicated. The best civil time to use currently is UTC.

While considering precise time keeping, a location can change its timezone (UTC+X) with a short or long notice. One used 14 days for example.
Another rule is leap seconds that are inserted.

The IANA timezone database is preferred to update local date time.