Question

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

Answer 1

The local time at this meridians is taken as the standard time for the whole country. It is known as the INDIAN STANDARD TIME IST because the local time of place which are on meridians are bound to differ that we need a standard meridians (IST)

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.