US - India Time Difference

The United States and India sit on opposite sides of the globe, separated by between 9 hours 30 minutes (ET during DST) and 13 hours 30 minutes (Hawaii) of time difference. The Indian Standard Time meridian at 82.5 degrees east, set at the Madras (now Chennai) Observatory in 1906, gives India a single year-round UTC+5:30 offset. The US, by contrast, spans six civilian timezones (Eastern, Central, Mountain, Pacific, Alaska, Hawaii) plus the no-DST quirk of Arizona, plus the territories.

Time differences shift twice a year because the US observes Daylight Saving Time and India does not. DST in the US runs from the second Sunday of March to the first Sunday of November, a 33-week stretch when the gap to India shrinks by one hour. Most of Arizona stays on Mountain Standard Time year-round, however, which means the AZ-IST gap is locked at 12 hours 30 minutes - the easiest US gap to remember.

Indian Standard Time was established in 1906 at the Madras Observatory and adopted nationally on 1 September 1906. Before that, three separate Indian civil times - Bombay Time, Madras Time, and Calcutta Time - made cross-country railway timetables a clerical nightmare. The Great Indian Peninsular Railway and the East Indian Railway both lobbied for unification. The 82.5 degree east meridian runs through Mirzapur in Uttar Pradesh and produces the exact UTC+5:30 offset still in use in 2026.

US timezones were established by the Standard Time Act of 1918, signed by Woodrow Wilson on 19 March of that year. Before 1918 each US city ran on its own local solar time, anchored to its own city hall - the Pennsylvania Railroad alone had to deal with 49 different local times in 1872. The 1918 act created the four contiguous-US zones; Alaska and Hawaii were added with statehood in 1959.

Daylight Saving Time was popularised by the New Zealand entomologist George Hudson in 1895 and by the English builder William Willett in 1907. Germany adopted DST on 30 April 1916 to save coal during the First World War. The US followed in 1918, repealed it in 1919, reintroduced War Time in 1942, and finally made it permanent under the Uniform Time Act of 1966. The most recent change was the 2007 Energy Policy Act extending DST to its current schedule.

India never adopted DST. The Indian government considered it during the 1962 Sino-Indian war and again during the 1971 Bangladesh war, but concluded that India's near-equatorial latitude provides almost the same daylight every day of the year, so shifting clocks would yield little benefit and considerable disruption to the railways, schools, and ports. The National Physical Laboratory in New Delhi maintains the IST signal using a network of caesium-fountain clocks traceable to international atomic time UTC.

The India-US technology corridor relies on these gap numbers daily. The IT services giants - Infosys, TCS, Wipro, HCL, Cognizant, Tech Mahindra, Mphasis, LTIMindtree - run dedicated Eastern shift (5 PM - 2 AM IST) and Central shift (6 PM - 3 AM IST) teams that overlap with US business hours. Knowing the exact gap for each US zone is fundamental to designing those shifts. This page provides the gap at a glance with a live readout that respects DST automatically.