Question

what is the mean of Indian standard time why do we need Standard Meridian in India

Answer 1

since Indian is a very large country, it needs a uniformity in time. 

If their will different times at different places, then it would be a lot confusing. Hence to remove this confusion, the Meridian 82'30 Degrees passing near Allahabad is taken as the standard meridian.

The significance of standard meridian of India is that Standard meridian is used as the standard time for whole country.

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.