Indian Standard Time

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Location of Mirzapur and the 82.5° E longitude that is used as the reference longitude for Indian Standard Time
Location of Mirzapur and the 82.5° E longitude that is used as the reference longitude for Indian Standard Time

Indian Standard Time (IST) is the time observed throughout India, with a time offset of UTC+5:30. India does not observe daylight saving time, (DST) 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.[1] In military and aviation time, IST is designated E* ("Echo-Star").[2]

Indian Standard Time is calculated on the basis of 82.5° E longitude. This line passes through several major Indian cities, however the Vindhyachal town, just west of the town of Mirzapur near Allahabad in the state of Uttar Pradesh is most cited. The longitude difference between Vindhyachal and the United Kingdom's Royal Observatory at Greenwich translates to an exact time difference of 5 hours 30 minutes. Local time is calculated from a clock tower at the Allahabad Observatory (25.15° N 82.5° E) though the official time-keeping devices are entrusted to the National Physical Laboratory, in New Delhi.[3]

Contents

[edit] History

One of the earliest descriptions of standard time in India appeared in the 4th century CE astronomical treatise Surya Siddhanta. Postulating a spherical earth, the book defined the prime meridian, or zero longitude, as passing through Avanti, the ancient name for the historic city of Ujjain ( 23°10′58″N, 75°46′38″E), and Rohitaka, the ancient name for Rohtak (28°54′N, 76°38′E), a city near the historic battle-field of Kurukshetra.[4]

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 ...[5]

The day used by ancient Indian astronomers began at sunrise at the prime meridian of Ujjain,[6] and was divided into smaller time units in the following manner:[7]

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 astronomical month, consists of 30 days.

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.[8] The Surya Siddhanta also described a method of converting local time to the standard time of Ujjain.[5] 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 in both lunar and solar units.[9] For example, the Jantar Mantar observatory built by Maharaja Sawai Jai Singh in Jaipur in 1733 contains large sundials, up to 90 ft (27 m) high, which were used to accurately determine the local time.

Astronomer John Goldingham is credited with the establishment of the current fractional time zone (UTC+5:30).
Astronomer John Goldingham is credited with the establishment of the current fractional time zone (UTC+5:30).

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 ( 13°5′24″N, 80°18′30″E) as 5 hours 30 minutes ahead of Greenwich Mean Time as the local standard time. This 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 was attached to a gun that was fired at 8 p.m. daily to announce that "all was well" with IST.[10] Time-keeping support for shipping activities in Bombay Harbour was provided by the Colaba Observatory in Bombay, which was established in 1826.[11]

Most towns in India retained their own local time until a few years after the introduction of the 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 Presidencies of British India, assumed special importance, and was gradually adopted by the nearby provinces and princely states. In the 19th century, clocks were kept in synchronisation through by telegraph – for example the railways synchronised their clocks thorough a time signal that was sent from the head office or the regional headquarters at a specified time every day.[12]

In 1884, the International Meridian Conference in Washington, D.C. set up uniform time zones across the world. It was decided that India would have two time zones, with Calcutta using the 90th east meridian and Bombay the 75° E meridian. Calcutta time was set at 5 hours 30 minutes 21 seconds ahead of GMT, while Bombay time was 4 hours 51 minutes ahead.[13] By the late 1880s, many railway companies began to use Madras time (known as "Railway time") as an intermediate time between the two zones. Another time zone, Port Blair mean time, was established at Port Blair, the capital of the Andaman and Nicobar Islands in the Bay of Bengal. The Port Blair mean time was set to 49 minutes 51 seconds ahead of Madras time.[14]

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. This 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.[12]

IST in relation with the bordering nations
IST in relation with the bordering nations

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.[12]

After independence in 1947, the 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.[12] The Central observatory was moved from Chennai to a location near Mirzapur, so that it would be as close to UTC +5:30 as possible.

During the Sino–Indian War of 1962 and the Indo–Pakistani Wars of 1965 and 1971, daylight saving was briefly used to reduce civilian energy consumption.[1]

[edit] Problems

In 2001, the government established a four–member committee under the Ministry of Science and Technology to examine the need for multiple time zones and daylight saving.[3] The findings of the committee, which were presented to Parliament in 2004 by the Minister for 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."[15]

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 do allow the Central and State governments to define and set the local time for a particular industrial area.[16]

[edit] Time signals

Official time signals are generated by the Time and Frequency Standards Laboratory at the National Physical Laboratory in New Delhi, for both commercial and official use. The signals are based on atomic clocks and are synchronised with the worldwide system of clocks that support the Coordinated Universal Time.

Features of the Time and Frequency Standards Laboratory include:[17]

The exact time is broadcast over the state–owned All India Radio and Doordarshan television network. Telephone companies have dedicated phone numbers connected to mirror time servers that also relay the precise time. Another increasingly popular means of obtaining the time is through Global Positioning System (GPS) receivers.[18]

[edit] See also

[edit] References

  1. ^ a b India Time Zones. Greenwich Mean Time (GMT). Retrieved on 2006-11-25.
  2. ^ Military and Civilian Time Designations. Greenwich Mean Time (GMT). Retrieved on 2006-12-02.
  3. ^ a b Sen, Ayanjit (2001-08-21). India investigates different time zones. BBC News. Retrieved on 2006-11-25.
  4. ^ Schmidt, Olaf H. (1944). The Computation of the Length of Daylight in Hindu Astronomy. Isis, 35(3):205–211. The University of Chicago Press. Retrieved on 2006-11-29.
  5. ^ a b Burgess, Ebenezer. 1858–1860. "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).
  6. ^ Swerdlow, N. 1973. "A Lost Monument of Indian Astronomy." Isis. 64(2):239–243.
  7. ^ Das, Sukumar Ranjan. 1928. "The Equation of Time in Hindu Astronomy">, The American Mathematical Monthly, 35(10):540–543. Retrieved 1 December 2006.
  8. ^ Piepoli, M. 1997. "Origin of Respiratory Sinus Arrhythmia in Conscious Humans." Circulation. 95:1813–1821. Retrieved 1 December 2006.
  9. ^ Tomczak, Matthias (2004-07-15). Lecture 7: Living with the seasons—the calendar problem. Lectures on Science, civilization and society, Flinders University, Australia. Retrieved on 2006-12-01.
  10. ^ History of Indian Time (IST). Greenwich Mean Time (GMT). Retrieved on 2006-11-25.
  11. ^ History of Indian Institute of Geomagnetism. National Informatics Centre (2006-10-10). Retrieved on 2006-11-25.
  12. ^ a b c d Odds and Ends. Indian Railways Fan Club. Retrieved on 2006-11-25.
  13. ^ Indian Time Zones (IST). Project Gutenberg. International Conference Held at Washington for the Purpose of Fixing a Prime Meridian and a Universal Day. October, 1884 Protocols of the Proceedings. Retrieved on 2006-11-25.
  14. ^ Note on the earthquake of 31 December 1881, Records of the Geological Survey of India,, XVII(2), 47–53, 1884. Cooperative Institute for Research in Environmental Sciences (CIRES). Retrieved on 2006-11-25.
  15. ^ Standard Time for Different Regions. Department of Science and Technology] (2004-07-22). Retrieved on 2006-11-25.
  16. ^ A matter of time. National Resource Centre for Women. Retrieved on 2006-11-25.
  17. ^ Indian Time Today (IST). Greenwich Mean Time (GMT). Retrieved on 2006-11-25.
  18. ^ Satellites for Navigation. Press Information Bureau, Government of India. Retrieved on 2006-11-25.

[edit] External links