Bombay Time was one of the two official time zones established in British India in 1884 . The time zone was established during the International Meridian Conference held at Washington , D.C. in the United States in 1884 . It was then decided that India would have two time zones , with Calcutta ( now Kolkata ) using the 90th meridian east and Bombay ( now Mumbai ) the 75th meridian east . Bombay Time was set at 4 hours and 51 minutes ahead of Greenwich Mean Time ( GMT )
International Meridian Conference
International Meridian Conference
Bombay Time