> We ask "what time is sunrise?", and "when will the days start getting longer?". We like "noon" to be when the sun is highest in the sky. All those things are what UTC is designed for.
The first thing is for time zones, inclusive of DST/Summer Time/etc. The second thing is for calendrical reform, which we've basically stopped doing now that the Gregorian calendar is as widespread as it's going to be. Leap seconds are for this:
> Currently the Earth runs slow at roughly 2 milliseconds per day. After 500 days, the difference between the Earth rotation time and the atomic time would be 1 second. Instead of allowing this to happen, a leap second is inserted to bring the two times closer together.
The "error" induced by the Earth slowing amounts to 12 minutes over the course of one thousand years.
The first thing is for time zones, inclusive of DST/Summer Time/etc. The second thing is for calendrical reform, which we've basically stopped doing now that the Gregorian calendar is as widespread as it's going to be. Leap seconds are for this:
https://tycho.usno.navy.mil/leapsec.html
> Currently the Earth runs slow at roughly 2 milliseconds per day. After 500 days, the difference between the Earth rotation time and the atomic time would be 1 second. Instead of allowing this to happen, a leap second is inserted to bring the two times closer together.
The "error" induced by the Earth slowing amounts to 12 minutes over the course of one thousand years.