Why India Runs on a Single Time Zone

India spans nearly 29 degrees of longitude but runs on a single clock, IST, set at UTC+5:30.

Before 1906, Bombay, Calcutta and Madras each kept their own local time, up to 39 minutes apart.

IST was fixed at 82°30'E near Mirzapur and adopted on 1 January 1906; Bombay clung to Bombay Time until 1955.

Assam's tea estates still quietly run on 'Chai Bagan Time', one hour ahead of IST.

A 2018 CSIR-NPL study proposed splitting India into IST-I and IST-II to save daylight and power.