The Allahabad Observatory, located in

Jhusi Jhusi or Jhunsi is a town in Prayagraj district in the Indian state of Uttar Pradesh. It was formerly called Pratishthan Pur or Puri. The place is also noted for being one of the Neolithic sites that provides some of the earliest evidence of ...

, a suburb of

Prayagraj 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 ...

(formerly Allahabad),

Uttar Pradesh Uttar Pradesh ( ; UP) is a States and union territories of India, state in North India, northern India. With over 241 million inhabitants, it is the List of states and union territories of India by population, most populated state in In ...

, India, is the centre responsible for maintaining the

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 translates to an exact time difference of 5 hours and 30 minutes 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) i.e. UTC+05:30. Sits right at 25.15°N, 82.5°E, lining up with the meridian they picked for India’s one time zone. The National Physical Laboratory (NPL) in

New Delhi New Delhi (; ) is the Capital city, capital of India and a part of the Delhi, National Capital Territory of Delhi (NCT). New Delhi is the seat of all three branches of the Government of India, hosting the Rashtrapati Bhavan, New Parliament ...

regulates the real precise time stuff with atomic clocks, but this observatory’s was tasked to figure local time as a reference point.

History

Pre-IST Timekeeping in India

Before the adoption of a unified time zone, India used localised time systems, with towns setting clocks based on their longitude. The introduction of railways in the 1850s necessitated standardised time for scheduling. In 1792, the

East India Company The East India Company (EIC) was an English, and later British, joint-stock company that was founded in 1600 and dissolved in 1874. It was formed to Indian Ocean trade, trade in the Indian Ocean region, initially with the East Indies (South A ...

established the

Madras Observatory The Madras Observatory was an astronomical observatory which had its origins in a private observatory set up by William Petrie in 1786 and later moved and managed by the British East India Company from 1792 in Madras (now known as Chennai). The ...

Chennai Chennai, also known as Madras (List of renamed places in India#Tamil Nadu, its official name until 1996), is the capital city, capital and List of cities in Tamil Nadu by population, largest city of Tamil Nadu, the southernmost states and ...

, which became a key timekeeping center. By 1802, its astronomer,

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 ...

, calculated Madras’s longitude as 5 hours and 30 minutes ahead of

Greenwich Mean Time Greenwich Mean Time (GMT) is the local mean time at the Royal Observatory, Greenwich, Royal Observatory in Greenwich, London, counted from midnight. At different times in the past, it has been calculated in different ways, including being ...

(GMT), influencing early railway time standards.

Adoption of Indian Standard Time

In 1884, the

International Meridian Conference The International Meridian Conference was a conference held in October 1884 in Washington, D.C., in the United States, to determine a prime meridian for international use. The conference was held at the request of President of the United State ...

established global time zones, prompting

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 ...

to formalise timekeeping. Initially, two time zones were used: Bombay Time (GMT+4:51) and

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 ...

(GMT+5:53:20). In 1905, the meridian at 82.5°E, east of Allahabad, was selected for a single time zone, and Indian Standard Time (IST), set at UTC+05:30, was officially adopted on 1 January 1906. This meridian was chosen for its central location between India’s western (UTC+05:00) and northeastern (UTC+06:00) extremities. After independence in 1947, IST became the sole time zone, with Kolkata and Mumbai phasing out local times by 1948 and 1955, respectively.

Establishment of the Allahabad Observatory

The Allahabad Observatory was likely established around 1905-1906 to support IST’s implementation, aligning with the 82.5°E meridian. Historical records indicate the central timekeeping observatory was relocated from Chennai to a site in Allahabad district, possibly near Shankargarh Fort. Specific details about its establishment remain sparse, but its creation coincided with the standardisation of IST.

Geography

The Allahabad Observatory is located in

, at 25.15°N, 82.5°E, directly on the 82.5°E longitude, the reference meridian for IST. This longitude, near

Mirzapur Mirzapur () is a city in Uttar Pradesh, India. It is known for its carpets and brassware industries, and the tradition of kajari and birha music. Straddled by the Kaimur extension of Vindhya mountains, it served as the headquarters of t ...

, about from Prayagraj, was selected for its central position within India’s longitudinal span (68.7°E to 97.25°E). The location balances time differences across India, where sunrise varies by nearly two hours between eastern and western regions.

Operations

The Allahabad Observatory calculates local time based on its longitude, serving as a reference for IST.It is equipped with a clock tower for local time determination. However, the National Physical Laboratory (NPL) in New Delhi manages official timekeeping, using Cesium atomic clocks and a Hydrogen maser for precision, accurate to one second in 300,000 years. It is not a public attraction, unlike the Jawahar Planetarium in Prayagraj, contributing to its low visibility. Timekeeping Mechanisms The observatory’s clock tower computes local time at 82.5°E, synchronised with the IST meridian. NPL’s Time and Frequency Metrology Section generates IST using atomic clocks and disseminates it via satellite, radio, and television networks, including All India Radio and Doordarshan. Telecommunication companies uses the precise time signals from NPL’s servers. The observatory also coordinates with India’s National Measurement Institute (NMI), under the

Council of Scientific and Industrial Research The Council of Scientific and Industrial Research (CSIR; IAST: ''vaigyanik tathā audyogik anusandhāna pariṣada'') is a research and development (R&D) organisation in India to promote scientific, industrial and economic growth. Headquarter ...

(CSIR). NPL ensures IST’s traceability to international standards like Coordinated Universal Time (UTC). Administrative oversight may involve the Department of Science and Technology (DST), though specific details are undocumented.

Significance

The Allahabad Observatory is integral to India’s timekeeping system. IST’s single time zone simplifies coordination across India’s 29° longitudinal span, supporting railways, telecommunications, and governance. The observatory’s establishment marked India’s shift to standardised time, driven by colonial infrastructure and modernisation needs. IST ensures consistent scheduling for transportation and communication networks. This observatory supports NPL’s alignment of IST with global time standards.

References

{{coord missing, Uttar Pradesh Astronomical observatories in India Buildings and structures in Prayagraj Tourist attractions in Prayagraj