Calcutta time was one of the two time zone

Time zone

A time zone is a region on Earth that has a uniform standard time for legal, commercial, and social purposes. In order for the same clock time to always correspond to the same portion of the day as the Earth rotates , different places on the Earth need to have different clock times...

s established in British India in 1884. It was established during the International Meridian Conference

International Meridian Conference

The International Meridian Conference was a conference held in October 1884 in Washington, D.C., in the United States to determine the Prime Meridian of the world. The conference was held at the request of U.S. President Chester A...

 held at Washington, D.C in the United States

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

. It was then decided that India were to have two time zones, with Calcutta (now Kolkata

Kolkata

Kolkata , formerly known as Calcutta, is the capital of the Indian state of West Bengal. Located on the east bank of the Hooghly River, it was the commercial capital of East India...

) would use the 90th meridian east

90th meridian east

The meridian 90° east of Greenwich is a line of longitude that extends from the North Pole across the Arctic Ocean, Asia, the Indian Ocean, the Southern Ocean, and Antarctica to the South Pole.The Ninety East Ridge is named after the meridian....

 and Bombay (Mumbai

Mumbai

Mumbai , formerly known as Bombay in English, is the capital of the Indian state of Maharashtra. It is the most populous city in India, and the fourth most populous city in the world, with a total metropolitan area population of approximately 20.5 million...

) the 75th meridian east

75th meridian east

The meridian 75° east of Greenwich is a line of longitude that extends from the North Pole across the Arctic Ocean, Asia, the Indian Ocean, the Southern Ocean, and Antarctica to the South Pole....

. Calcutta time was set at 5 hours, 30 minutes, and 21 seconds in advance of GMT.

It remained in effect even after Indian Standard Time

Indian Standard Time

Indian Standard Time is the time observed throughout India and Sri Lanka, with a time offset of UTC+05:30. India does not observe daylight saving time or other seasonal adjustments, although DST was used briefly during the Sino–Indian War of 1962 and the Indo–Pakistani Wars of 1965 and 1971...

 (IST) was adopted on January 1, 1906. In 1948, Calcutta time was completely abandoned in favour of IST.

See also

• Indian Standard Time
  Indian Standard Time
  Indian Standard Time is the time observed throughout India and Sri Lanka, with a time offset of UTC+05:30. India does not observe daylight saving time or other seasonal adjustments, although DST was used briefly during the Sino–Indian War of 1962 and the Indo–Pakistani Wars of 1965 and 1971...
  
  
• Bombay time
• Port Blair mean time
  Port Blair mean time
  Port Blair mean time was the time zone of the Andaman and Nicobar Islands of India in the Bay of Bengal. The time zone was set up during the early 19th century remained in effect until January 1, 1906 as the Indian Standard Time became the official time of India.-See also:* Indian Standard Time*...