Question

The local time at Greenwich is considered to be international standard time

Answer 1

The local time at green which is called international standard time......
India have its own time called int Indian standard time as the meridian passes through the latitude of 82°30`E

Answer 2

Since the time of industrial revolution in the beginning of the 19th century, the concept of timeline has been introduced in order to ease of the calculation of the time.

The Greenwich is considered as the prime time location of this timeline.

As the England once had colonies in most of the parts of the world and Greenwich is situated in the middle of the UK so they have selected this place as the prime in time zone.