Question

How is standard time of a place determined. Answer in breaf.

Answer 1

If you mean how is Greenwich time determined…

To oversimplify a bit, there are two kinds of Greenwich time. One is UTC, which is kept by atomic clocks. The other is determined by the passage of the stars above the turning earth. Once you figure out what sidereal time is at the moment, the conversion to mean solar time is simple.

So two time systems, which naturally don’t line up perfectly — the earth doesn’t match the atomic clocks perfectly. We want UTC to stay close to earth time, so when it creeps ahead a half-second or so they announce: at the end of the year UTC will have a leap second — we’ll stop the UTC clock for one second — to allow earth time to move just ahead of UTC. There have been 30+ leap seconds since that system started in 1972.