India is under a single time zone

There is only one time zone for all of India. India does not observe any form of daylight saving time or any other seasonal adjustments to the time. With India’s western and eastern borders more than 2,000 km (1,250 miles) far from each other, India could well have three time zones, like China; however, India chooses to have a single time zone across the whole country.

India’s time zones were established in 1884. Originally there were two time zones, the Bombay time and Calcutta time. Bombay continued to have a different time until 1955.

In the very early days of railways in India, local time was observed at each large city, in common with practice in most other countries at the time. Because of their importance as commercial and economic centers, Bombay time and Calcutta time assumed special importance and were followed for many official purposes in the late 19th century, effectively forming two time zones for British India. Calcutta time was 5 hours, 30 minutes, and 21 seconds in advance of GMT (Greenwich Mean Time), while Bombay Time was 4 hours and 51 minutes ahead of GMT. Many railway companies, however, standardized on using Madras time as being in between Bombay and Calcutta times.

Standard time zones can be defined by geometrically subdividing the Earth’s spheroid into 24 moons, bordered by meridians each 15° of longitude apart. The local time in neighboring zones would differ by one hour. However, political boundaries, geographical practicalities, and convenience of inhabitants can result in irregularly shaped zones.