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| − | [[Image:IST-Mirzapur.svg|thumb|Location of [[Mirzapur]] and the 82.5° E longitude that is used as the reference longitude for Indian Standard Time]]
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| − | '''Indian Standard Time''' ('''IST''') represents the [[time zone|time]] observed throughout [[India]], with a [[time offset]] of [[UTC+5:30]]. India opted out of observing [[daylight saving time]], (DST) or other seasonal adjustments, although briefly using DST during the [[Sino-Indian War|Sino–Indian War of 1962]] and the [[Indo-Pakistani War of 1965|Indo–Pakistani Wars of 1965]] and [[Indo-Pakistani War of 1971|1971]].<ref name="timez">{{cite web | url =http://wwp.india-time.com/indian-time-zones.htm | title =India Time Zones | accessdate =2006-11-25| work=[http://wwp.greenwichmeantime.com Greenwich Mean Time (GMT)]}} </ref> In military and aviation time, '''E*''' ("Echo-Star") designates IST.<ref>{{cite web | url = http://wwp.greenwichmeantime.com/info/timezone.htm
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| − | | title = Military and Civilian Time Designations | accessdate =2006-12-02| work=[http://wwp.greenwichmeantime.com Greenwich Mean Time (GMT)]}} </ref>
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| − | Indian Standard Time calculates on the basis of 82.5° E [[longitude]], just west of the town of [[Mirzapur]], near [[Allahabad]] in the state of [[Uttar Pradesh]]. The longitude difference between Mirzapur and the [[United Kingdom]]'s [[Royal Observatory, Greenwich|Royal Observatory]] at [[Greenwich]] translates to an exact time difference of 5 hours 30 minutes. A [[clock tower]] at the [[Allahabad Observatory]] ({{coor d|25.15|N|82.5|E|}}) calculates local time, though the [[National Physical Laboratory, India|National Physical Laboratory]], in [[New Delhi]] has been entrusted with the official time-keeping devices.<ref name="bbc">{{cite web | url=http://news.bbc.co.uk/2/hi/south_asia/1501252.stm |title=India investigates different time zones|accessdate=2006-11-25 |last=Sen |first=Ayanjit |date=2001-08-21 |work=[http://news.bbc.co.uk BBC News]}}</ref>
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| − | ==History==
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| − | One of the earliest descriptions of ''standard time'' in India appeared in the [[4th century]] CE [[Hindu astronomy|astronomical]] treatise [[Surya Siddhanta]]. Postulating a [[Spherical Earth|spherical earth]], the book defined the [[Prime Meridian|prime meridian]], or zero longitude, as passing through ''[[Avanti (India)|Avanti]]'', the ancient name for the historic city of [[Ujjain]] ({{coor dms|23|10|58|N|75|46|38|E}}), and ''Rohitaka'', the ancient name for [[Rohtak]] ({{coor dm|28|54|N|76|38|E}}), a city near the historic battle-field of [[Kurukshetra]].<ref>{{cite web| url=http://www.jstor.org/view/00211753/ap020353/02a00020/0| title=The Computation of the Length of Daylight in Hindu Astronomy| accessdate=2006-11-29| last=Schmidt| first=Olaf H.|date=1944| work= Isis, '''35'''(3):205–211| publisher=The University of Chicago Press}}</ref> <blockquote>Situated upon the line which passes through the haunt of the demons ([[equator]] and 76° E) and the mountain which is the seat of the gods (the [[North Pole]]), are Rohitaka and Avanti ...<ref name=burgess>Burgess, Ebenezer. 1858–1860. [http://www.jstor.org/view/00030279/ap020003/02a00030/0 "Translation of the Surya-Sikddhanta, A Text-Book of Hindu Astronomy; With Notes, and an Appendix."] ''Journal of the American Oriental Society'', '''6''':141–498. (pages 183–186).</ref></blockquote>
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| − | The day used by ancient Indian astronomers began at sunrise at the prime meridian of Ujjain,<ref> Swerdlow, N. 1973. [http://www.jstor.org/view/00211753/ap010172/01a00100/0 "A Lost Monument of Indian Astronomy."] ''Isis''. '''64'''(2):239–243.</ref> which they divided into smaller time units in the following manner:<ref> Das, Sukumar Ranjan. 1928. [http://www.jstor.org/view/00029890/di991110/99p1463g/0 "The Equation of Time in Hindu Astronomy">, ''The American Mathematical Monthly''], '''35'''(10):540–543. Retrieved 1 December 2006.</ref> <blockquote> Time that is measurable is that which is in common use, beginning with the ''prāṇa'' (or, the time span of one breath). The ''pala'' contains six ''{{Unicode|prāṇas}}''. The ''ghalikā'' is 60 ''palas'', and the ''{{Unicode|nakṣatra ahórātra}}'', or astronomical day, contains 60 ''ghalikās''. A ''{{Unicode|nakṣatra māsa}}'', or [[sidereal month|astronomical month]], consists of 30 days.</blockquote>
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| − | Measuring a day as twenty four hours, the smallest time unit, ''prāṇa'', or one respiratory cycle, equals four seconds, a value consistent with the ''normal breathing frequency'' of fifteen breaths/min used in modern medical research.<ref>Piepoli, M. 1997. [http://circ.ahajournals.org/cgi/content/full/95/7/1813 "Origin of Respiratory Sinus Arrhythmia in Conscious Humans."] ''Circulation''. '''95''':1813–1821. Retrieved 1 December 2006.</ref> The Surya Siddhanta also described a method of converting local time to the standard time of Ujjain.<ref name=burgess/> Despite those early advances, only astronomers commonly used standard time. For most of [[History of India|India's history]], ruling kingdoms kept their own local time, typically using the [[Hindu calendar]] in both [[sidereal time|lunar]] and [[solar time|solar]] units.<ref>{{cite web|url=http://www.es.flinders.edu.au/~mattom/science+society/lecture7.html| title=Lecture 7: Living with the seasons—the calendar problem|accessdate=2006-12-01| last=Tomczak| first=Matthias|date=2004-07-15 |publisher=Lectures on Science, civilization and society, Flinders University, Australia}}</ref> For example, the [[Jantar Mantar (Jaipur)|Jantar Mantar]] observatory built by [[Jai Singh II of Amber|Maharaja Sawai Jai Singh]] in [[Jaipur]] in 1733 contains large [[sundial]]s, up to 90 ft (27 m) high, used to accurately determine the local time.
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| − | [[Image:John Goldingham.png|thumb|Astronomer [[John Goldingham]] is credited with the establishment of the current fractional time zone (UTC+5:30).]]
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| − | In 1792, the [[British East India Company]] established the [[Madras Observatory]] in [[Chennai]] (then Madras), largely due to the efforts of the British sailor–astronomer [[Michael Topping]]. In 1802, John Goldingham, appointed as the first official astronomer of the Company in India, established the longitude of Madras ({{coor dms|13|5|24|N|80|18|30|E|}}) as 5 hours 30 minutes ahead of [[Greenwich Mean Time]] as the local [[standard time]]. That marked the first use of the current time zone, and departure from the earlier standard of the day beginning at sunrise; now it started at midnight. The clock in the observatory attached to a gun that fired at 8 p.m. daily to announce that "all was well" with IST.<ref>{{cite web|url=http://wwp.greenwichmeantime.com/time-zone/asia/india/time/history-indian-time.htm |title=History of Indian Time (IST) |accessdate=2006-11-25 |work=[http://wwp.greenwichmeantime.com/ Greenwich Mean Time (GMT)]}}</ref> Time-keeping support for shipping activities in [[Mumbai Harbour|Bombay Harbour]] was provided by the Colaba Observatory in Bombay, which was established in 1826.<ref>{{cite web|url=http://iigs.iigm.res.in/history.htm |title=History of Indian Institute of Geomagnetism|accessdate=2006-11-25|date=2006-10-10|publisher=[[National Informatics Centre]]}}</ref>
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| − | Most towns in India retained their own local time until a few years after the introduction of the [[Rail transport in India|railways]] in the 1850s, when the need for a unified time zone became apparent. Local time in [[Mumbai]] (then Bombay) and [[Kolkata]] (then Calcutta), as headquarters of the two largest [[Presidency City|Presidencies of British India]], assumed special importance, the nearby provinces and [[princely state]]s gradually adopted the standard. In the 19th century, [[telegraph]] kept the clocks in synchronization– for example the railways synchronized their clocks thorough a time signal sent from the head office or the regional headquarters at a specified time every day.<ref name="Princely states">
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| − | {{cite web|url=http://www.irfca.org/faq/faq-misc.html |title=Odds and Ends |accessdate=2006-11-25 |work=[http://www.irfca.org Indian Railways Fan Club]}}</ref>
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| − | In 1884, the [[International Meridian Conference]] in [[Washington, D.C.]] set up uniform time zones across the world, India receiving two time zones, with Calcutta using the 90th east meridian and Bombay the 75° E meridian. The Conference set [[Calcutta time]] at 5 hours 30 minutes 21 seconds ahead of GMT, while setting [[Bombay time]] at 4 hours 51 minutes ahead.<ref>{{cite web|url=http://www.gutenberg.org/files/17759/17759-h/17759-h.htm |title=Indian Time Zones (IST) |accessdate=2006-11-25 |work=[http://www.gutenberg.org/ Project Gutenberg]| publisher=International Conference Held at Washington for the Purpose of Fixing a Prime Meridian and a Universal Day. October, 1884 Protocols of the Proceedings}}</ref> By the late 1880s, many railway companies began to use [[Madras time]] (known as "[[Railway time]]") as an intermediate time between the two zones. The Britist colonial government established another time zone, [[Port Blair mean time]], established at [[Port Blair]], the capital of the [[Andaman and Nicobar Islands]] in the [[Bay of Bengal]]. They set Port Blair mean time to 49 minutes 51 seconds ahead of Madras time.<ref>{{cite web|url=http://cires.colorado.edu/~bilham/Oldham1881account.htm |title=Note on the earthquake of 31 December 1881, Records of the Geological Survey of India,, XVII(2), 47–53, 1884 |accessdate=2006-11-25 |work=Cooperative Institute for Research in Environmental Sciences (CIRES)}}</ref>
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| − | [[British Raj|British India]] officially adopted the standard time zones in 1905, when picking the meridian passing east of Allahabad at 82.5° E longitude as the central meridian for India, corresponding to a single time zone for the country. That came into force on 1 January 1906, also applying to [[Sri Lanka]] (then [[Ceylon]]). Calcutta time remained as an official, separate time zone until 1948.<ref name="Princely states"/>
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| − | [[Image:IST-CIA-TZ.png|thumb|IST in relation with the bordering nations]]
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| − | In 1925, the government began relaying time synchronization through omnibus telephone systems and control circuits to organisations that needed to know the precise time. That continued until the 1940s, when the government began to broadcast time signals using the radio.<ref name="Princely states"/>
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| − | After [[Indian independence movement|independence in 1947]], the [[Government of India|Indian government]] established IST as the official time for the whole country, although Kolkata and Mumbai retained their own local time for a few more years.<ref name="Princely states"/> The Central observatory moved from Chennai to a location near [[Mirzapur]], as close as possible to UTC +5:30.
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| − | During the Sino–Indian War of 1962 and the Indo–Pakistani Wars of 1965 and 1971, the government resorted briefly to daylight saving time as a way of reducing civilian energy consumption.<ref name="timez"/>
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| − | ==Problems==
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| − | <!--A single, large time zone has been assumed to cost more, {{Fact|date=October 2007}} by requiring rescheduling of events to make them compatible with the rest of the zone or with the day's cycle.{{clarifyme}}—>The country's east–west distance of more than 2,000 km (1,200 miles) covers over 28 degrees of longitude, resulting in the sun rising and setting almost two hours earlier in the north-eastern [[Seven Sister States]] than in the [[Rann of Kutch]] in the far west. 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; the government rejected the recommendations adopted.<ref name="bbc"/><ref>{{cite web|url=http://www.hinduonnet.com/mp/2002/01/07/stories/2002010700130300.htm |title=A matter of time |accessdate=2006-11-25 |last=S. Muthiah |date=2002-01-07 |work=[http://www.thehindubusinessline.com The Hindu Business Line] |publisher=[[The Hindu]] Group}}</ref>
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| − | In 2001, the government established a four–member committee under the [[Ministry of Science and Technology (India)|Ministry of Science and Technology]] to examine the need for multiple time zones and daylight saving.<ref name="bbc"/> The findings of the committee, presented to [[Parliament of India|Parliament]] in 2004 by the Minister for Science and Technology, [[Kapil Sibal]], recommended maintaining the current 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."<ref>{{cite web|url=http://dst.gov.in/admin_finance/un-sq1007.htm |title=Standard Time for Different Regions |accessdate=2006-11-25 |date=2004-07-22 |work=Department of Science and Technology]}}</ref>
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| − | Though the government has consistently refused to split the country into multiple time zones, provisions in labour laws such as the ''Plantations Labour Act, 1951'' allow the Central and State governments to define and set the local time for a particular industrial area.<ref>{{cite web|url=http://nrcw.nic.in/shared/sublinkimages/19.htm |title=A matter of time |accessdate=2006-11-25 |work=National Resource Centre for Women}}</ref>
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| − | An August 2007 article in the ''[[Current Science]]'' [[Academic journal|journal]] estimated that the evening peak energy demand could be reduced by as much as 16 percent by setting Indian Standard Time six hours ahead of Universal Coordinated Time instead of the present 5.5 hours.<ref>[http://www.hindu.com/2007/08/11/stories/2007081158212200.htm Time to move forward to meet India’s energy crunch? by Divya Gandhi] August 11, 2007 [[The Hindu]]</ref><ref>{{cite journal |last=Ahuja |first=Dilip R.|coauthors=Sen Gupta, D. P. and Agrawal, V. K. |year=2007 | month=August 10 |title= Energy savings from advancing the Indian Standard Time by half an hour |journal=[[Current Science]] |volume=93 |issue=3 |pages= pp. 298-302 |id= |url=http://www.ias.ac.in/currsci/aug102007/298.pdf}}</ref> According to the authors, the money value of the savings accrued as a result of the time change would be in the range of Rs 1,000 crore every year.<ref>[http://timesofindia.indiatimes.com/Scientists_suggest_pushing_IST_to_save_energy/articleshow/2331397.cms Scientists suggest pushing IST to save energy] 2 September, 2007 [[The Times of India]]</ref>
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| − | ==Time signals==
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| − | The [[Time and Frequency Standards Laboratory]] at the National Physical Laboratory in New Delhi generate official time signals for both commercial and official use. The signals, based on [[atomic clock]]s, synchronize with the worldwide system of clocks that support the [[Coordinated Universal Time]].
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| − | Features of the Time and Frequency Standards Laboratory include:<ref>{{cite web|url=http://wwp.greenwichmeantime.com/time-zone/asia/india/time/indian-time-today.htm |title=Indian Time Today (IST) |accessdate=2006-11-25 |work=[http://wwp.greenwichmeantime.com/ Greenwich Mean Time (GMT)]|}}</ref>
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| − | *Four [[caesium]] and [[rubidium]] atomic clocks;
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| − | *[[High frequency]] broadcast service operating at 10 MHz under call sign ''ATA'' to synchronize the user clock within a millisecond;
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| − | *[[Indian National Satellite System]] satellite–based standard time and frequency broadcast service, which offers IST correct to ±10 microsecond and frequency calibration of up to ±10<sup>−10</sup>; and
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| − | *Time and frequency calibrations made with the help of [[picosecond|pico–]] and [[nanosecond]]s time interval [[frequency counter]]s and [[phase (waves)|phase]] recorders.
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| − | The state–owned [[All India Radio]] and [[Doordarshan]] television network broadcast the exact time. Telephone companies have dedicated phone numbers connected to [[mirror (computing)|mirror]] [[time server]]s that also relay the precise time. Obtaining the time through [[Global Positioning System]] (GPS) receivers offers another increasingly popular method. .<ref>{{cite web|url=http://pib.nic.in/release/rel_print_page.asp?relid=19703 |title=Satellites for Navigation |accessdate=2006-11-25 |work=[http://pib.nic.in Press Information Bureau, Government of India]|}}</ref>
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| − | ==See also==
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| − | *[[Equation of time]]
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| − | *[[Hindu astrology]]
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| − | *[[International Atomic Time]]
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| − | *[[Terrestrial Time]]
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| − | *[[Time zone]] ([[List of time zones|list]])
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| − | *[[zoneinfo]]
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| − | ==Notes==
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| − | <div class="references-small" style="-moz-column-count:2; column-count:2;">
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| − | <references />
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| − | </div>
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| − | ==References==
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| − | * Bartky, Ian R. 2007. One time fits all the campaigns for global uniformity. Stanford, Calif: Stanford University Press. ISBN 9780804756426
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| − | * Blaise, Clark. 2000. Time lord Sir Sandford Fleming and the creation of standard time. New York: Pantheon Books. ISBN 9780375401763
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| − | * Vij, Brij Bhushan. 1982. Towards a unified technology if time standard went metric. New Delhi: Soni Book Agency (India). OCLC: 9392166
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| − | ==External links==
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| − | *[http://www.nplindia.ernet.in/time.php National Physical Laboratory]. Retrieved November 1, 2007.
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| − | *[http://wwp.greenwichmeantime.com/time-zone/asia/india/time/history-indian-time.htm History of India Time (IST)]. Retrieved November 1, 2007.
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| − | *[http://wwp.greenwichmeantime.com/time-zone/asia/india/time/indian-time-today.htm India Time Today.]. Retrieved November 1, 2007.
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| − | [[Category:Physical sciences]]
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| − | [[Category:Astronomy]]
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