Is IST the same as Sri Lanka time?

Sri Lanka uses the same UTC offset but calls its standard Sri Lanka Standard Time. The IANA zone is Asia/Colombo. For scheduling, they are identical.

Does India observe daylight saving time?

No. India has never observed DST at the national level. Wartime experiments were abandoned. The offset stays UTC+5:30 all year.

Why is India's time zone half an hour off?

The 82.5°E meridian, chosen in 1906, falls between the longitudes that would produce whole-hour offsets. It was a compromise between the older Bombay Time and Calcutta Time.

What does IST stand for in an international meeting invite?

IST can mean India Standard Time, Irish Standard Time (UTC+1, summer), or Israel Standard Time (UTC+2, winter). Check the context. If the meeting spans Europe and Asia, clarify which IST is meant.

What time is it in IST right now?

See the live clock on the IST Time Now page.

How do I convert IST to my local time?

Use the IST Converter tool. Enter any time and date to see the equivalent in major global time zones, with their DST rules applied.

What Is India Standard Time (IST)? UTC+5:30 Explained

India Standard Time (IST) is the time zone observed across India and Sri Lanka, fixed year-round at UTC+5:30. It is based on the 82.5°E meridian passing through Mirzapur, Uttar Pradesh, and is maintained by atomic clocks at the CSIR-National Physical Laboratory in New Delhi.

What time zone is IST?

India runs on one time zone. The offset from Coordinated Universal Time (UTC) is +5 hours and 30 minutes, and the clock never moves. No daylight saving. No seasonal shifts. That half-hour offset puts IST in a small group: Nepal (UTC+5:45), Iran (UTC+3:30), Afghanistan (UTC+4:30), and roughly a dozen others worldwide that reject the whole-hour convention.

The abbreviation "IST" does triple duty. India Standard Time is the one used in Asia. Irish Standard Time (UTC+1, summer only) and Israel Standard Time (UTC+2, winter only) share the same three letters. A meeting invite that says "IST" without a city name is a 50/50 gamble. Always confirm which continent the call is on.

Why is IST UTC+5:30?

UTC is the reference. IST runs 5 hours and 30 minutes ahead of it. Noon in London means 5:30 PM in Mumbai, Delhi, Chennai, and everywhere else under the Indian flag.

That offset is fixed. India has never observed national daylight saving time. Wartime experiments in 1942-1945 and again during the 1962 Sino-Indian war were brief and abandoned. Today, the offset holds steady through January and July.

The half hour traces back to a railway compromise. Before 1906, India kept multiple local times. Bombay Time sat at UTC+4:51. Calcutta Time ran at UTC+5:53:20. Railways defaulted to Madras Time, and the chaos pushed the colonial administration to act. On 1 January 1906, IST was adopted at UTC+5:30, pinned to the 82.5° east longitude meridian that passes through Mirzapur, near Prayagraj in Uttar Pradesh. The meridian split the difference between the two older standards.

IST vs GMT: the trap

"IST is GMT+5:30" is true only part of the year. GMT is a time zone, the local time in London during winter. UTC is the standard. When the UK switches to British Summer Time (BST, UTC+1), the gap between London and India shrinks to 4.5 hours. Convert from UTC, not from a city's current local time. If you hardcode "GMT+5:30" into a summer meeting invite, you arrive 30 minutes late.

Where is IST used?

IST covers India and Sri Lanka. Two countries, one offset, two legally distinct time standards.

India stretches roughly 30 degrees of longitude from Gujarat to Arunachal Pradesh. A span that wide could justify two time zones. The one-nation-one-time policy, adopted at independence in 1947 and reaffirmed since, overrides that logic. The political choice creates a lopsided daylight experience in the northeast. Tea gardens in Assam have responded with an informal workaround: "Tea Garden Time", which runs an hour ahead of IST, is a local practice, not a legal time zone. Check with the relevant garden or estate for current usage.

Sri Lanka adopted the UTC+5:30 offset in 2006 after a brief experiment with UTC+6. Sri Lanka Standard Time uses the IANA zone Asia/Colombo. India uses Asia/Kolkata. Same offset, different legal names.

What is the IANA time zone for India?

The Internet Assigned Numbers Authority (IANA) time zone database is the canonical source for computer time zone definitions. India is Asia/Kolkata. Sri Lanka is Asia/Colombo. Both resolve to UTC+5:30 and share the CLDR metazone label "India".

Selecting Asia/Kolkata on a device tells the operating system three things: the offset is UTC+5:30, daylight saving never applies, and the display name is "India Standard Time". The zone is named after Kolkata because it is the largest city in eastern India, not because the city controls the clock.

Major cities in this zone include Mumbai (population 12,691,836), Delhi (11,034,555), Bengaluru (8,495,492), Hyderabad (6,993,262), Chennai (4,681,087), and Kolkata (4,631,392).

IST in computing

The CSIR-National Physical Laboratory in New Delhi maintains IST using caesium atomic clocks. NPL operates public NTP (Network Time Protocol) servers. Enterprise systems and telecom networks in India typically point to NPL's stratum 1 servers for clock synchronisation.

Unix and Linux systems run their system clock in UTC. Applications display local time by applying the Asia/Kolkata rule. The Unix timestamp, seconds since 1 January 1970, is always UTC. Converting to IST means adding 5 hours and 30 minutes.

ISO 8601 expresses IST as +05:30. 2:00 PM IST on 21 June 2026 is written 2026-06-21T14:00:00+05:30.

Quick reference: IST at a glance

Property	Detail
Abbreviation	IST
Full name	India Standard Time
UTC offset	UTC+5:30, fixed
Daylight saving	Not observed
IANA zone (India)	Asia/Kolkata
IANA zone (Sri Lanka)	Asia/Colombo
Reference meridian	82.5°E (Mirzapur)
Timekeeper	CSIR-National Physical Laboratory, New Delhi
Countries	India, Sri Lanka