Question

Why is there a time difference of 5 hrs and 30mins between IST and GMT ?

Answer 1

The basic answer is Indian Standard Time is calculated on the basis of 82.5° E longitude, which is just west of the town of Mirzapur, near Allahabad in the state of Uttar Pradesh. The longitude difference between Mirzapur and the United Kingdom's Royal Observatory at Greenwich translates to an exact time difference of 5 hours 30 minutes.

Answer 2

It's very simple.... GMT (Greenwich mean time) is the base or reference longitude with which we can calculate the exact time of any place on any longitude ... If GMT is 00.00hrs means , it is 12 midnight at London (where GMT is located).. India is 5.30 hrs ahead of GMT... Hence the time corresponding to India to 5.30 AM the following day....

Also remember the longitudes lying to left of the GMT will be lacking in time while longitydes lying right of the GMT will be gaining in time....