> either UTC or a Unix timestamp (which afaik is essentially the same as using UTC except that it's less easy for most people to read at a glance) UTC has leap

> either UTC or a Unix timestamp (which afaik is essentially the same as using UTC except that it's less easy for most people to read at a glance) UTC has leap seconds, unix timestamp doesn't. It's defined to have 86400 seconds per day, so there's no place to put a leap second. Instead, it either duplicates a timestamp or does "leap smearing" - slightly changing the duration of a second around where the leap second is.