Question

What determines where the time 0 start from? And then , -2hr, -4hr,+2hr +4hr, etc? The time differences? Why does it start at 0 start there?

Answer 1

The Greenwich time was originally implemented because Europeans think they control the world and can tell others where and how their time zones shall be drawn. In essence it was just put there because European scientists decided to put it there. There is actually a line drawn there today for tourists. The different time zones are usually decided by the countries within the zones.