Calcutta time was one of the two time zones established in British India in 1884 . It was established during the International Meridian Conference held at Washington , D.C. in the United States . It was decided that India had two time zones : Calcutta ( now Kolkata ) would use the 90th meridian east and Bombay ( Mumbai ) the 75th meridian east
International Meridian Conference
International Meridian Conference
Calcutta Time