India India, officially the Republic of India, is a country in South Asia. It is the List of countries and dependencies by area, seventh-largest country by area; the List of countries by population (United Nations), most populous country since ...

uses only one time zone (even though it spans two geographical

time zones Time is the continuous progression of existence that occurs in an apparently irreversible succession from the past, through the present, and into the future. It is a component quantity of various measurements used to sequence events, to compa ...

) across the whole nation and all its territories, called

Indian Standard Time Indian Standard Time (IST), sometimes also called India Standard Time, is the time zone observed throughout the Republic of India, with a time offset of UTC+05:30. India does not observe daylight saving time or other seasonal adjustments. I ...

(IST), which equates to UTC+05:30, i.e. five and a half hours ahead of

Coordinated Universal Time Coordinated Universal Time (UTC) is the primary time standard globally used to regulate clocks and time. It establishes a reference for the current time, forming the basis for civil time and time zones. UTC facilitates international communicat ...

(UTC). India does not currently observe

daylight saving time Daylight saving time (DST), also referred to as daylight savings time, daylight time (Daylight saving time in the United States, United States and Daylight saving time in Canada, Canada), or summer time (British Summer Time, United Kingdom, ...

(DST or summer time). The official time signal is given by the Time and Frequency Standards Laboratory. The

IANA time zone database The tz database is a collaborative compilation of information about the world's time zones and rules for observing daylight saving time, primarily intended for use with computer programs and operating systems. Paul Eggert has been its editor an ...

contains only one zone pertaining to India, namely ''Asia/Kolkata''. The date and time notation in India shows some peculiarities. Mysore Clocktower - clock face

Background

History

Ancient India

The 4th century CE

astronomical Astronomy is a natural science that studies celestial objects and the phenomena that occur in the cosmos. It uses mathematics, physics, and chemistry in order to explain their origin and their overall evolution. Objects of interest include ...

treatise

Surya Siddhanta The ''Surya Siddhanta'' (; ) is a Sanskrit treatise in Indian astronomy dated to 4th to 5th century,Menso Folkerts, Craig G. Fraser, Jeremy John Gray, John L. Berggren, Wilbur R. Knorr (2017)Mathematics Encyclopaedia Britannica, Quote: "(...) i ...

postulated a

spherical Earth Spherical Earth or Earth's curvature refers to the approximation of the figure of the Earth as a sphere. The earliest documented mention of the concept dates from around the 5th century BC, when it appears in the writings of Ancient Greek philos ...

. The book described a custom of the

prime meridian A prime meridian is an arbitrarily chosen meridian (geography), meridian (a line of longitude) in a geographic coordinate system at which longitude is defined to be 0°. On a spheroid, a prime meridian and its anti-meridian (the 180th meridian ...

, or zero longitude, as passing through '' Avanti'', the ancient name for the historic city of

Ujjain Ujjain (, , old name Avantika, ) or Ujjayinī is a city in Ujjain district of the Indian state of Madhya Pradesh. It is the fifth-largest city in Madhya Pradesh by population and is the administrative as well as religious centre of Ujjain ...

, and ''Rohitaka'', the ancient name for

Rohtak Rohtak () is a city and the administrative headquarters of the Rohtak district in the Indian state of Haryana. It lies north-west of New Delhi and south of the state capital Chandigarh on NH 9 (old NH 10). Rohtak forms a part of the Nationa ...

(), a city near the

Kurukshetra Kurukshetra () is a city and administrative headquarters of Kurukshetra district in the Indian state of Haryana. It is also known as Dharmakshetra ("Realm of duty") and as the "Land of the Bhagavad Gita". Legends According to the Puranas ...

. The day used by ancient Indian astronomers began at sunrise at the prime meridian of Ujjain, and was divided into smaller time units in the following manner: Taking a day to be 24 hours, the smallest time unit, ''prāṇa'', or one respiratory cycle, equals 4 seconds, a value consistent with the ''normal breathing frequency'' of 15 breaths/min used in modern medical research. The Surya Siddhanta also described a method of converting local time to the standard time of Ujjain. Despite these early advances, standard time was not widely used outside astronomy. For most of India's history, ruling kingdoms kept their own local time, typically using the

Hindu calendar The Hindu calendar, also called Panchangam, Panchanga (), is one of various lunisolar calendars that are traditionally used in the Indian subcontinent and Southeast Asia, with further regional variations for social and Hindu religious purposes ...

in both lunar and

solar Solar may refer to: Astronomy * Of or relating to the Sun ** Solar telescope, a special purpose telescope used to observe the Sun ** A device that utilizes solar energy (e.g. "solar panels") ** Solar calendar, a calendar whose dates indicate t ...

units. For example, the Jantar Mantar observatory built by Maharaja Sawai Jai Singh in

Jaipur Jaipur (; , ) is the List of state and union territory capitals in India, capital and the List of cities and towns in Rajasthan, largest city of the north-western States and union territories of India, Indian state of Rajasthan. , the city had ...

in 1733 contains large

sundial A sundial is a horology, horological device that tells the time of day (referred to as civil time in modern usage) when direct sunlight shines by the position of the Sun, apparent position of the Sun in the sky. In the narrowest sense of the ...

s, up to high, which were used to accurately determine the local time.

During British colonial rule

In 1802 Madras Time was set up by

John Goldingham John Goldingham (1767 - July 1849) was the first official astronomer of the Madras Observatory, appointed in 1802. Goldingham was also an architect and surveyor who headed the Madras Survey School which later grew into the Guindy Engineering Col ...

and this was later used widely by the railways in India. Local time zones were also set up in the important cities of

Bombay Mumbai ( ; ), also known as Bombay ( ; its official name until 1995), is the capital city of the Indian States and union territories of India, state of Maharashtra. Mumbai is the financial centre, financial capital and the list of cities i ...

and

Calcutta Kolkata, also known as Calcutta (List of renamed places in India#West Bengal, its official name until 2001), is the capital and largest city of the Indian States and union territories of India, state of West Bengal. It lies on the eastern ba ...

and as Madras time was intermediate to these, it was one of the early contenders for an Indian standard time zone. Though

British India The provinces of India, earlier presidencies of British India and still earlier, presidency towns, were the administrative divisions of British governance in South Asia. Collectively, they have been called British India. In one form or another ...

did not officially adopt the standard time zones until 1905, when the meridian passing east of

Allahabad Prayagraj (, ; ISO 15919, ISO: ), formerly and colloquially known as Allahabad, is a metropolis in the Indian state of Uttar Pradesh.The other five cities were: Agra, Kanpur, Kanpur (Cawnpore), Lucknow, Meerut, and Varanasi, Varanasi (Benar ...

at 82.5° E longitude was picked as the central meridian for India, corresponding to a single time zone for the country ( UTC+05:30).

came into force on 1 January 1906, and also applied to

Sri Lanka Sri Lanka, officially the Democratic Socialist Republic of Sri Lanka, also known historically as Ceylon, is an island country in South Asia. It lies in the Indian Ocean, southwest of the Bay of Bengal, separated from the Indian subcontinent, ...

(then

Ceylon Sri Lanka, officially the Democratic Socialist Republic of Sri Lanka, also known historically as Ceylon, is an island country in South Asia. It lies in the Indian Ocean, southwest of the Bay of Bengal, separated from the Indian subcontinent, ...

). However, Calcutta Time was officially maintained as a separate time zone until 1948 and Bombay Time until 1955. In 1925, time synchronisation began to be relayed through omnibus telephone systems and control circuits to organisations that needed to know the precise time. This continued until the 1940s, when time signals began to be broadcast using the radio by the government. Briefly during World War II, clocks under Indian Standard Time were advanced by one hour, referred to as War Time. This provision lasted from 1 September 1942, to 15 October 1945.

After independence

After independence in 1947, the

Indian government The Government of India (ISO: Bhārata Sarakāra, legally the Union Government or Union of India or the Central Government) is the national authority of the Republic of India, located in South Asia, consisting of 36 states and union territor ...

established IST as the official time for the whole country, although Mumbai and Kolkata retained their own local time for a few more years. In 2014

Assam Assam (, , ) is a state in Northeast India, northeastern India, south of the eastern Himalayas along the Brahmaputra Valley, Brahmaputra and Barak River valleys. Assam covers an area of . It is the second largest state in Northeast India, nor ...

ese politicians proposed following a daylight-saving schedule that would be ahead of IST by an hour, but as of March 2020 it has not been approved by the central government. ''Plantations Labour Act of 1951'' allows the union and state governments to define and set the local time for particular industrial areas. Due to this, in regions of

, tea gardens follow a separate time zone, known as the ''Chaibagan'' or ''Bagan'' time ('Tea Garden Time'), which is one hour ahead of IST. However, IST remains the only officially used time.

Former practices

Former timezones

Earlier time zones, no longer in use after the adoption of a standardized time zone across India, were: * Bombay Time ( UTC+04:51) *

Calcutta Time Calcutta Time was one of the two official time zones established in British India in 1884. It was established during the International Meridian Conference held at Washington, D.C. in the United States. It was decided that India had two time zones ...

( UTC+05:53:20) * Madras Time ( UTC+05:21:14) * Port Blair mean time ( UTC+06:10:37)

Former daylight saving

India and the

Indian subcontinent The Indian subcontinent is a physiographic region of Asia below the Himalayas which projects into the Indian Ocean between the Bay of Bengal to the east and the Arabian Sea to the west. It is now divided between Bangladesh, India, and Pakista ...

observed ''"daylight saving (DST)"'' during the Second World War, from 1942 to 1945. During the

Sino-Indian War The Sino–Indian War, also known as the China–India War or the Indo–China War, was an armed conflict between China and India that took place from October to November 1962. It was a military escalation of the Sino–Indian border dispu ...

of 1962 and the Indo–Pakistani Wars of

1965 Events January–February * January 14 – The First Minister of Northern Ireland and the Taoiseach of the Republic of Ireland meet for the first time in 43 years. * January 20 ** Lyndon B. Johnson is Second inauguration of Lynd ...

and

1971 * The year 1971 had three partial solar eclipses (Solar eclipse of February 25, 1971, February 25, Solar eclipse of July 22, 1971, July 22 and Solar eclipse of August 20, 1971, August 20) and two total lunar eclipses (February 1971 lunar eclip ...

, daylight saving was briefly used to reduce civilian energy consumption.

Present time zone

India uses UTC+5:30, referred to as Asia/Kolkata in the

References

{{Asia topic, Time in Geography of India Time in Asia