The longitudes which pass through a country or region, are used to fix the standard time for that country or region. In India, From Gujarat to Arunachal Pradesh, there is a time lag of about 2 hours. Hence, the Standard Meridian of India (82°30'E) passing through Mirzapur (in Uttar Pradesh) is taken as the standard time for the whole country. Because, different regions have different times, so to have one common time for the whole country, the time of Mirzapur has been selected as the Indian Standard Time (IST).