After independence in 1947, the Indian government established IST as the official time for the whole country, although Kolkata and Mumbai retained their own local time (known as Calcutta Time and Bombay Time) until 1948 and 1955, respectively [REF].
Daylight Saving Time (DST) was used briefly during the China-Indian War of 1962 and the Indo-Pakistani Wars of 1965 and 1971 [REF].