imported>Guccirajappan at 06:49, 22 August 2021

2021-08-22T06:49:19Z

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{{short description|Overview of the time zones used in India}}
[[File:IST-CIA-TZ.png|thumb|Time zones of [[South Asia]] (numbers are hours ahead of [[UTC]])]]

The [[India|Republic of India]] uses only one time zone (even though it spans across two geographical [[time zones]]) across the whole nation and all its territories, called [[Indian Standard Time]] (IST), which equates to [[UTC+05:30]], i.e. five and a half hours ahead of [[Coordinated Universal Time]] (UTC). India presently does not observe [[daylight saving time]] (DST or summer time).

The official time signal is given by the [[Time and Frequency Standards Laboratory]]. The [[IANA time zone database]] contains only one zone pertaining to India, namely ''Asia/Kolkata''. The [[date and time notation in India]] shows some peculiarities.

== Background ==
=== History ===

====Ancient India====
{{anchor | Hindu | Ancient }}
{{see also| Hindu units of time | History of measurement systems in India#Ancient | l2= History of measurement systems in India }}
[[File:HinduMeasurements.svg|thumb|200px|Hindu units of time—largely of ritual importance—displayed on a [[logarithmic scale]].]]

One of the earliest known 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 described the thousands years old customs of the [[Prime Meridian|prime meridian]], or zero longitude, as passing through ''[[Avanti (India)|Avanti]]'', the ancient name for the historic city of [[Ujjain]], and ''Rohitaka'', the ancient name for [[Rohtak]] ({{Coord|28|54|N|76|38|E|type:city|name=Rohitaka (Rohtak)}}), a city near the [[Kurukshetra]].<ref>{{cite journal| jstor=330729| title=The Computation of the Length of Daylight in Hindu Astronomy| last=Schmidt| first=Olaf H.|year=1944| journal= Isis | volume=35| issue=3| pages=205–211| publisher=The University of Chicago Press| doi=10.1086/358709| s2cid=145178197}}</ref>

The day used by ancient Indian astronomers began at sunrise at the prime meridian of Ujjain,<ref>{{cite journal|last1=Swerdlow|first1=N.|title=A Lost Monument of Indian Astronomy:Das heliozentrische System in der griechischen, persischen und indischen Astronomie B. L. van der Waerden|journal=Isis|date=January 1973|volume=64|issue=2|pages=239–243|doi=10.1086/351088|s2cid=146253100}}</ref> and was divided into smaller time units in the following manner:<ref name=das>{{cite journal|last1=Das|first1=Sukumar Ranjan|title=The Equation of Time in Hindu Astronomy|journal=The American Mathematical Monthly|date=December 1928|volume=35|issue=10|pages=540–543|doi=10.2307/2298168|jstor=2298168}}</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 ''prāṇas''. The ''ghalikā'' is 60 ''palas'', and the ''nakṣatra ahórātra'', or astronomical day, contains 60 ''ghalikās''. A ''nakṣatra māsa'', or [[sidereal month|astronomical month]], consists of 30 days.</blockquote>

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.<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>{{cite journal|last1=Burgess|first1=Ebenezer|title=Translation of the Surya-Siddhanta, A Text-Book of Hindu Astronomy; With Notes, and an Appendix|journal=Journal of the American Oriental Society|date=1858|volume=6|pages=183–186|doi=10.2307/592174|jstor=592174}}</ref> Despite these early advances, standard time was not widely used outside astronomy. 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|access-date=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, which were used to accurately determine the local time.

====During British colonial rule ====

In 1802 [[Madras Time]] was set up by [[John Goldingham]]<ref>{{Cite journal|editor=William Nicholson|title=Eclipses of the Satellites of Jupiter, observed by John Goldingham and under his Superintendence, at Madras, in the East Indies|journal=A Journal of Natural Philosophy, Chemistry, and the Arts|publisher=Stratford, Crown Court and Temple Bar|location=London|date=1809|volume=22|pages=153–156|url=https://books.google.com/books?id=xJAOjlQ6TNMC&q=madras+time++goldingham+1802&pg=PA153}}</ref> and this was later used widely by the railways in India.<ref name="Princely states"/> Local time zones were also set up in the important cities of [[Bombay]] and [[Calcutta]] and as Madras time was intermediate to these, it was one of the early contenders for an Indian standard time zone.<ref>{{Cite journal|title=On Time in India|journal=Proceedings of the Asiatic Society of Bengal|publisher=Asiatic Society of Bengal|location=Calcutta|date=April 1899|pages=49–55|url=https://books.google.com/books?id=kIIbAQAAIAAJ&q=%22madras+time%22&pg=PA51}}</ref><ref>{{Cite journal|title=On the Introduction of a Standard Time for India|journal=Proceedings of the Asiatic Society of Bengal|publisher=Asiatic Society of Bengal|location=Calcutta|date=June 1899|pages=62–66|url=https://books.google.com/books?id=kIIbAQAAIAAJ&q=%22Calcutta+time%22+%22madras+time%22&pg=PA63}}</ref> Though [[British Raj|British India]] did not officially adopt the standard time zones until 1905, when the meridian passing east of [[Allahabad]] 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]]). [[Indian Standard Time]] came into force on 1 January 1906, and also applied to [[Sri Lanka]] (then [[Ceylon]]). However, Calcutta Time was officially maintained as a separate time zone until 1948 and Bombay Time until 1955.<ref name="Princely states">{{cite web|url=http://www.irfca.org/faq/faq-misc.html |title=Odds and Ends |access-date=2006-11-25 |work= Indian Railways Fan Club}}</ref>

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.<ref name="Princely states"/> Briefly during World War II, clocks under Indian Standard Time were advanced by one hour, referred to as War Time. This provision lasted from September 1, 1942 to October 15, 1945.<ref>http://www.timeanddate.com/worldclock/timezone.html?n=54&syear=1925</ref>

====After independence====
After [[Indian independence movement|independence in 1947]], the [[Government of India|Indian government]] established IST as the official time for the whole country, although Mumbai and Kolkata retained their own local time for a few more years.<ref name="Princely states"/> In 2014 [[Assam]]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.<ref>[http://www.ndtv.com/article/india/india-gets-its-second-time-zone-as-assam-turns-its-clock-ahead-by-an-hour-466326 India may get its second time zone if Assam turns its clock ahead by an hour]</ref>

===Former practices ===
====Former timezones ====
{{anchor | TZ | Timezones |Former timezones }}

Older time zones, not in use any more since introduction of standardised same time zone across India, were:
*[[Bombay Time]] ([[UTC+04:51]])
*[[Madras Time]] ([[UTC+05:00|UTC+05:21:14]])
*[[Calcutta Time]] ([[UTC+05:30|UTC+05:53:20]])
*[[Port Blair mean time]] ([[UTC+06:00|UTC+06:10:37]])<ref>[http://cires.colorado.edu/~bilham/Oldham1881account.htm Oldham, R. D. Note on the earthquake of 31 December 1881, Records of the Geological Survey of India, XVII(2), 47-53, 1884.]</ref>

==== Former daylight saving ====
{{anchor | DST | Dst }}
India and the [[Indian subcontinent]] observed ''"daylight saving (DST)"'' during the Second World War, from 1942–1945. During the [[Sino-Indian War]] of 1962 and the [[Indo-Pakistani wars and conflicts|Indo–Pakistani Wars]] of [[Indo-Pakistani War of 1965|1965]] and [[Indo-Pakistani War of 1971|1971]], daylight saving was briefly used to reduce civilian energy consumption.{{Citation needed span|text=|date=December 2020}}

==Present time zone ==
India uses UTC+5:30,<ref name="Princely states"/> referred to as Asia/Kolkata in the [[Tz database|IANA time zone database]].

==Demand for changes ==
In 2014 [[Assam]]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.<ref>[http://www.ndtv.com/article/india/india-gets-its-second-time-zone-as-assam-turns-its-clock-ahead-by-an-hour-466326 India may get its second time zone if Assam turns its clock ahead by an hour]</ref>

==See also ==
* [[Date and time notation in India]]
* [[Hindu units of time]]
* [[History of measurement systems in India]]
* [[Daylight saving time]]
* [[Daylight saving time by country]]

==References==
{{reflist}}

{{Asia topic|Time in}}

[[Category:Time in India| ]]
[[Category:Time in Asia]]
[[Category:Time zones]]

Time in India - Revision history

imported>Guccirajappan at 06:49, 22 August 2021