| Indian Standard Time | |
|---|---|
| Time zone | |
| UTC offset | |
| IST | UTC+05:30 |
| Current time | |
| 07:11, 5 April 2025IST[refresh] | |
| Observance ofDST | |
| DST is not observed in this time zone. | |
Indian Standard Time (IST), sometimes also calledIndia Standard Time, is thetime zone observed throughout theRepublic of India, with atime offset ofUTC+05:30. India does not observedaylight saving time or other seasonal adjustments. Inmilitary and aviation time, IST is designatedE* ("Echo-Star").[1] It is indicated asAsia/Kolkata in theIANA time zone database.
The Indian Standard Time was adopted on 1 January 1906 during theBritish era with the phasing out of its precursorMadras Time (Railway Time),[2] and afterIndependence in 1947, theUnion government established IST as the official time for the whole country, althoughKolkata andMumbai retained their own local time (known asCalcutta Time andBombay Time) until 1948 and 1955, respectively.[3] The Central observatory was moved fromChennai to a location at Shankargarh Fort inAllahabad district, so that it would be as close toUTC+05:30 as possible.[4]
Daylight Saving Time (DST) was used briefly during theChina–India War of 1962 and the Indo-PakistaniWars of 1965 and1971.[5]
| Time Zone | UTC | Period | Purpose |
|---|---|---|---|
| Bombay Time | UTC+04:51 | 1884–1955 | Official |
| Calcutta Time | UTC+05:53:20 | 1884–1948 | Official |
| Chennai Time | UTC+05:21:14 | 1802–1906 | Railways |
| Port Blair mean time | UTC+06:10:37 | 19th century–1906 | Local |
Indian Standard Time is calculated from the reference longitude of IST at 82°30'E passing nearMirzapur Clock Tower.[6] In 1905, the meridian passing east of Allahabad was declared as a standard time zone forBritish India and was declared as IST in 1947 for theDominion of India.[7] This longitude of 82°30'E was chosen as thestandard meridian for the whole country[8] as it is located centrally betweenwestern India (local time UTC +05:00) andnortheastern India (local time UTC +06:00). Currently, theNational Physical Laboratory of India maintains the Indian Standard Time with the help of theAllahabad Observatory.[9]
The country's east–west distance of more than 2,933 kilometres (1,822 mi) covers over 29° of longitude, resulting in the sun rising and setting almost two hours earlier on India'seastern border than in theRann of Kutch in the far west. Inhabitants of thenortheastern states have to advance their clocks with the early sunrise to avoid the extra consumption of energy after daylight hours.[6]
In the late 1980s, a team of researchers proposed separating the country into two or three time zones to conserve energy. The binary system that they suggested involved a return to British-era time zones, but the recommendations were not adopted.[6][10]
In 2001, the government established a four-member committee under theMinistry of Science and Technology to examine the need for multiple time zones and daylight saving.[6] The findings of the committee, which were presented toParliament in 2004 by the Minister of Science and Technology,Kapil Sibal, did not recommend changes to the unified system, stating that 'the prime meridian was chosen with reference to a central station, and that the expanse of the Indian State was not large.'[11]
Though the government has consistently refused to split the country into multiple time zones, provisions in labour laws such as thePlantations Labour Act, 1951 allow the union and state governments to define and set the local time for a particular industrial area.[12] InAssam, tea gardens follow a separate time zone, known as theChaibagan orBagan time ('Tea Garden Time'), which is one hour ahead of IST.[13] Still, Indian Standard Time remains the only officially used time.
In 2014, Chief Minister of AssamTarun Gogoi started campaigning for another time zone forAssam and othernortheastern states of India.[14][15] However, the proposal would need to be cleared by theunion government.
In June 2017, theDepartment of Science and Technology (DST) indicated that it is once again studying the feasibility of two time zones for India. Proposals for creating an additional Eastern India Time (EIT atUTC+06:00), shifting default IST toUTC+05:00 and daylight saving (Indian Daylight Time for IST and Eastern India Daylight Time for EIT) starting on 14 April (Ambedkar Jayanti) and ending on 2 October (Gandhi Jayanti) was submitted to DST for consideration.[16][needs update]
Official time signals are generated by theTime and Frequency Standards Laboratory at the National Physical Laboratory inNew Delhi, for both commercial and official use. The signals are based onatomic clocks and synchronised with the worldwide system of clocks that supportCoordinated Universal Time.
Features of the Time and Frequency Standards Laboratory include:
IST is taken as the standard time as it passes through almost the centre of India. To communicate the exact time to the people, the exact time is broadcast over the nationalAll India Radio andDoordarshan television network. Telephone companies have dedicated phone numbers connected to mirrortime servers that also relay the precise time. Another increasingly popular means of obtaining the time is throughGlobal Positioning System (GPS) receivers.[17]
As part of theTimes Dissemination Project, which is overseen by theMinistry of Consumer Affairs, Food, and Public Distribution,NavIC will take the position of GPS as the reference time provider at the National Physical Laboratory from 2025. With an atomic clock in each of the four other centers—Ahmedabad,Bengaluru,Bhubaneswar, andGuwahati—the reference time from NavIC will be transmitted via anoptical fiber link from the Faridabad center. Indian Standard Time must be used as the exclusive time reference for official, commercial, administrative, and legal documents, according to draft regulations published by theDepartment of Consumer Affairs. Exceptions will be permitted for astronomy, navigation, and scientific research.[18][19]
