Indian Standard Time

About Indian Standard Time

  • Indian Standard Time(IST) represents the 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 of 1962 and the Indo–Pakistani Wars of 1965 and 1971.
  • In military and aviation time, E*(“Echo-Star”) designates IST.
  • 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 at Greenwich translates to an exact time difference of 5 hours 30 minutes.
  • A clock tower at the Allahabad Observatory (15° N 82.5° E) calculates local time, though the National Physical Laboratory, in New Delhi has been entrusted with the official time-keeping devices.

Indian Standard Time

History of IST

  • 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, the nearby provinces and princely states gradually adopted the standard.
  • In the 19th century, telegraphkept 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.
  • 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.
  • 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 British 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.
  • British Indiaofficially 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 January 1, 1906, also applying to Sri Lanka (then Ceylon). Calcutta time remained as an official, separate time zone until 1948.

IST in relation with the bordering nations

  • In 1925, the government began relaying time synchronization through omnibus telephone systems and control circuits to organizations that needed to know the precise time. That continued until the 1940s, when the government began to broadcast time signals using the radio.
  • 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.
  • The Central observatory moved from Chennai to a location near Mirzapur, as close as possible to UTC +5:30.
  • 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.

Issues with IST

  • 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
  • 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.
  • The findings of the committee, presented to 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.”
  • Though the government has consistently refused to split the country into multiple time zones, provisions in labour laws such as the Plantations Labour Act, 1951allow the Central and State governments to define and set the local time for a particular industrial area.
  • An August 2007 article in the Current Sciencejournal 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.
  • 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.

Time signals

  • 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 clocks, synchronize with the worldwide system of clocks that support the Coordinated Universal Time.
  • Features of the Time and Frequency Standards Laboratory include:
  • Four caesium and rubidium atomic clocks
  • High frequency broadcast service operating at 10 MHz under call sign ATA to synchronize the user clock within a millisecond
  • 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 ±10−10
  • Time and frequency calibrations made with the help of pico– and nanoseconds time interval frequency counters and phase recorders
  • The state–owned All India Radio and Doordarshan television network broadcast the exact time.
  • Telephone companies have dedicated phone numbers connected to mirror time servers that also relay the precise time.
  • Obtaining the time through Global Positioning System(GPS) receivers offers another increasingly popular method.