This day in the year 1947 saw the establishment of Indian Standard Time (IST) as the official time for the entire country. It is the time observed in India and Sri Lanka. It is denoted as E.
IST is observed with reference to 82.58° E longitude that passes precisely through Mirzapur in Uttar Pradesh. It is ahead of Greenwich Mean Time (GMT) by 05:30 hours, and is denoted as UTC+5:30.
Previously there were two time zones in India. An international conference held at Washington D.C., in the year 1884, to decide on a prime meridian for international use. Consequently, Calcutta time and Bombay time, were introduced. The two cities continued to follow their time zones until 1948 and 1955 respectively.
Another time zone, known as Madras time, was introduced in 1802 – long before the Calcutta and Bombay time zones. Since Madras time was very close in time to the current IST, railway companies began using it as an intermediate time zone between the two time zones. It is now referred to as the ‘railway time of India’.
