City history
Delhi transitioned from ancient local solar time and 18th-century masonry astronomical observatories to national time standardization under Indian Standard Time in 1906.
Chapter one
Earliest documented name
"Loose or slack (disputed etymology)"
Recorded in a 1170 CE Sanskrit inscription at Bijolia, Dhillika is the earliest firmly documented historical name for the urban settlement that grew into modern Delhi. Disputed etymologies link the name to the Prakrit word dhili, meaning loose, or to an ancient king named Dhillu.
Plain of Indra
Recorded in the ancient Indian epic Mahabharata as the capital of the Pandavas, tradition and archaeological finds associate Indraprastha with the Purana Qila site in eastern Delhi.
Loose or slack, or named after King Dhillu
Developed under Tomar Rajput rulers, the medieval city was inscribed as Dhillika in 1170 CE and Dhilli in 1276 CE, serving as the linguistic origin of modern Dilli or Delhi.
Abode of Shah Jahan
Established by fifth Mughal Emperor Shah Jahan as his capital in 1639, this grand walled city contained the Red Fort and Jama Masjid and is now called Old Delhi.
Anglicized form of Dilli / New capital city
King George V declared the shift of British India's capital from Calcutta to Delhi in 1911; the planned administrative area of New Delhi was formally inaugurated in 1931.
Chapter two
Delhi observed local solar time calculated at UTC+05:08:48 based on its central geographic meridian, while colonial administration relied on distinct local solar times across major regional hubs.
British India officially adopted Indian Standard Time at UTC+05:30 on January 1, 1906, establishing the 82.5°E meridian passing near Mirzapur to synchronize national railway schedules and telegraphic communications.
During World War II, British India temporarily advanced national clocks by one hour to UTC+06:30 between 1942 and 1945 as a daylight saving measure to save electrical power during wartime operations.
Following national independence in 1947, the Government of India reaffirmed UTC+05:30 as the official standard time zone for the entire republic, centralized administratively in Delhi.
Chapter three
Maharaja Sawai Jai Singh II of Jaipur completed the Jantar Mantar observatory in Delhi, featuring the massive Samrat Yantra sundial designed to measure precise local solar time and track celestial movements.
Delhi synchronized its administrative and railway timekeeping with Indian Standard Time (UTC+05:30), ending dependence on disparate regional solar times across northern India.
At the Delhi Durbar, King George V announced the transfer of the capital of India from Calcutta to Delhi, leading to the planning and construction of New Delhi.
The CSIR-National Physical Laboratory in New Delhi was tasked with maintaining UTC(NPLI) using cesium atomic clocks to generate and disseminate official Indian Standard Time.
The commercial launch of the Delhi Metro introduced automated, high-precision electronic timing standards across India's largest urban rail network, standardizing mass transit travel schedules.