Why 82°30’E has been selected as the standard meridian of India?
The Earth has been divided into 24 time zones of one hour each. Each of these zones covers 15 degrees of longitude. As the local time differs by 4 minutes at every longitude, it would create a lots of confusion regarding time for any country. From Gujarat to Arunachal Pradesh, there is a time lag of about two hours.
Hence, time along the Standard Meridian of India (82° 30’ E) passing through Mirzapur (in Uttar Pradesh) is taken as the standard time for the whole country. Otherwise different regions of India would have different time. So, to avoid this problem 82°30’ E has been selected as the one common standard time for the whole country and this is called Indian Standard Time (IST).