The maximum longitudinal extent of India is about 30°. We all know that the local time of a place is directly related to its longitude. The Earth completes one rotation around its axis in one day. In other words it cover 360° in 24 hours. This comes out to be four minutes for every 1° of longitude or one hour for 15° of longitude. As there is difference of 30° longitude between the easternmost point in Arunanchal Pradesh and Dwarka in Gujarat the difference of local time, it will create a lot of confusion regarding radio and television programmes, air flights and railway time table etc. In order to avoid this type of confusion regarding time, the
  82° 30' E longitude is taken as the standard meridian of India