What Is IST?
IST stands for India Standard Time, a timezone at UTC+05:30 (5 hours and 30 minutes ahead of Coordinated Universal Time) from Coordinated Universal Time. It is used in India. The IANA Time Zone Database, the authoritative global reference used by operating systems, programming languages, and web services, records this zone under the identifier Asia/Kolkata. IANA identifiers are unambiguous: Asia/Kolkata maps to exactly one timezone in the world, unlike the abbreviation IST, which has 3 possible interpretations (see below). IST does not observe Daylight Saving Time: the UTC+05:30 offset is fixed year-round.
Reference meridian: 82.5°E longitude, passing through Mirzapur, Uttar Pradesh. Official timekeeping authority: National Physical Laboratory of India (CSIR-NPL), New Delhi.
Other Meanings of IST
The abbreviation IST is not unique to India Standard Time. It is also used for:
- Irish Standard Time (UTC+01:00): Ireland during summer (last Sunday March to last Sunday October).
- Israel Standard Time (UTC+02:00): Israel year-round (no DST since 2013).
This ambiguity is why ISO 8601, the international standard for date and time : does not use abbreviations at all. It uses numeric offsets like +05:30 or IANA identifiers like Asia/Kolkata. When writing times for international audiences, always include the UTC offset alongside the abbreviation to prevent misreading.
Current IST Time and Date
The clock above shows the current IST time: 16:17 on Friday, March 6, 2026. It is calculated using the browser's Intl.DateTimeFormat API with the IANA identifier Asia/Kolkata, the same source your phone and laptop use for timezone conversions. The time updates every second. If you need a static reference, note that IST is always UTC+05:30 from UTC : it never observes Daylight Saving Time.
IST to UTC Conversion
To convert IST to UTC: subtract 05:30 from the IST time. Example: 14:00 IST = 09:30 UTC. In ISO 8601 format, a IST timestamp is written as 2026-03-06T16:17:00+05:30. This format is unambiguous and machine-readable, always prefer it over abbreviation-only notation for data exchange.
Cities in the IST Timezone
Major cities that observe IST (UTC+05:30) include:
These cities all share the IANA zone identifier Asia/Kolkata (or a zone with the same current offset). Click any city link to see its live clock, DST status, and time difference from major world cities.
DST Transition Dates for IST
India Standard Time does not observe Daylight Saving Time. The offset is fixed at UTC+05:30 year-round. This makes IST one of the most predictable timezones for international scheduling, the offset you see today is the offset you will see in six months. India abolished DST experimentation after a brief period during World War II and has maintained UTC+05:30 continuously since independence in 1947.
DST Variants: IST vs Standard Time
IST does not observe Daylight Saving Time. The UTC+05:30 offset applies every day of the year, no seasonal adjustment, no clock changes. India formally abolished DST experimentation after a brief period during World War II. IST has been fixed at UTC+5:30 continuously since independence in 1947.
History of India Standard Time
India's single timezone has a specific historical origin. In 1802, British colonial astronomer John Goldingham established local mean time at the Madras Observatory (now Chennai), using it as the reference for the subcontinent. By 1884, two competing zones existed: Bombay Time (UTC+4:51) and Calcutta Time (UTC+5:53). The 1884 International Meridian Conference in Washington, D.C. formalized Greenwich as the Prime Meridian, pushing India toward a unified reference.
In 1905, the meridian at 82.5 degrees East longitude, passing through Mirzapur, Uttar Pradesh, was selected as the basis for a unified Indian time. The UTC+5:30 offset was officially established in 1906, splitting the difference between the earlier Bombay and Calcutta zones. Upon independence in 1947, India formally declared this offset as India Standard Time. The National Physical Laboratory of India (CSIR-NPL), based in New Delhi, maintains the official IST signal broadcast and coordinates with the International Bureau of Weights and Measures (BIPM).
A 2018 CSIR-NPL study proposed dividing India into two zones: IST-I (UTC+5:30, for most of the country) and IST-II (UTC+6:30, for northeastern states). The proposal was not adopted. India's geographic anomaly remains: the country spans approximately 3,000 km (30 degrees of longitude) east to west, meaning solar noon varies by nearly 2 hours between the easternmost and westernmost points, comparable to Utah and New York sharing a single timezone across the United States.
Why Timezone Abbreviations Are Ambiguous
ISO 8601, the international standard for date and time notation, does not define timezone abbreviations. IANA, which maintains the authoritative timezone database, uses geographic identifiers (America/New_York, Asia/Kolkata) rather than abbreviations. Abbreviations emerged from railway timetables and military communications in the 19th and early 20th centuries, before any international standardization effort.
The result is a patchwork. EST is used in North America for UTC-05:00 and in parts of Australia for UTC+10:00 or UTC+11:00. IST covers three different UTC offsets across three continents. CST applies to UTC-06:00 (US Central), UTC+08:00 (China), and UTC-05:00 (Cuba). Even GMT, seemingly the anchor, is used differently than UTC: GMT is a timezone designation specific to the UK and West Africa, while UTC is the mathematical standard maintained by atomic clocks. They share the same offset (UTC+00:00) but are not interchangeable in formal contexts.
Best practice: always write the numeric offset alongside the abbreviation (IST (UTC+05:30)) or use ISO 8601 format for machine-readable timestamps. For the IANA identifier, use Asia/Kolkata.
Converting IST to Major World Timezones
Current conversions from IST (16:17) to other major timezones:
- New York (EST/EDT): 05:47 (UTC-05:00)
- London (GMT/BST): 10:47 (UTC+00:00)
- Dubai (GST): 14:47 (UTC+04:00)
- Singapore (SGT): 18:47 (UTC+08:00)
- Tokyo (JST): 19:47 (UTC+09:00)
- Sydney (AEST/AEDT): 21:47 (UTC+11:00)