Question

what is the mean by Indian standard time why do we need a standard Meridian

Answer 1

IST is a meridian of longitude. It is at a distance of 82.5° from the Greenwich towards the EAST. It passes through ALLAHABAD which is the approximate centre of India.


IMPORTANCE:
This meridian of longitude (82.5°E) is 5 and a half hours ahead from the time at Greenwich. India has the IST as it's standard time because if it wouldn't have been there, the country would have difference of 2 hours (as India is a large country and has a large East-west extent --- there's a difference of 2 hours from Gujarat in the west to Assam in the east). Hence, IST is an important meridian of longitude.

Answer 2

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The time of a place depends on the longitude that passes through it. Therefore, the standard time for each country is usually taken as the time of the central meridian that passes through it.Thus, we need a standard meridian for the country. In India 82 ½ °E longitude determines the standard time.