Learn the basics
Why India has only one time zone, and why it is UTC+5:30
India stretches nearly 3,000 km from east to west, wide enough for two time zones, yet the whole country runs on Indian Standard Time. Here is where IST came from, why it ends in half an hour, what it costs the Northeast, and what it means when you work with the rest of the world.
Key takeaways
- IST is UTC+5:30 everywhere in India, all year. India has no daylight saving time.
- The half hour comes from geography: IST is set by the 82°30′E meridian near Mirzapur, and 82.5° ÷ 15° per hour = 5.5 hours.
- IST dates from 1906, but Calcutta kept its own time until 1948 and Bombay until 1955.
- In June the sun rises around 4 AM IST in Arunachal Pradesh and after 6 AM in Gujarat. A 2018 study by CSIR-NPL proposed a second zone, UTC+6:30, for the Northeast; it has not been adopted.
On this page
Indian Standard Time in one paragraph
Indian Standard Time (IST) is 5 hours 30 minutes ahead of Coordinated Universal Time (UTC+5:30). It is used in every state and union territory, from Gujarat to Arunachal Pradesh and the Andaman and Nicobar Islands, and it never changes: India has no daylight saving time. The official time is kept by the CSIR-National Physical Laboratory in New Delhi.
Right now it is in India, on .
Why the half hour?
Time zones are based on the Earth turning 15 degrees of longitude every hour. Most countries picked a meridian that is a multiple of 15°, which gives whole-hour offsets. India’s standard meridian is 82°30′ East, a line that passes close to Mirzapur in Uttar Pradesh, roughly through the middle of the country. 82.5 ÷ 15 = 5.5, so the clock is set 5 hours 30 minutes ahead of Greenwich.
Several neighbours also have unusual offsets, which is why “just add an hour” rarely works in South Asia:
- IndiaIST · UTC+5:30
- NepalUTC+5:45
- Sri LankaUTC+5:30
- BangladeshUTC+6
- PakistanUTC+5
- MyanmarUTC+6:30
A short history of IST
In the 19th century, Indian cities kept their own local times, and the railways ran on Madras time. In 1905 the colonial government chose the 82°30′E meridian through Mirzapur as the basis for a single Indian Standard Time, and it came into use on 1 January 1906.
Not everyone switched. Calcutta, then a major commercial capital, kept its own Calcutta Time until 1948, and Bombay Time survived until 1955. Since then IST has been the only official time in the country.
The problem: India is wide
India spans about 29 degrees of longitude, from roughly 68°E in Gujarat to 97°E in Arunachal Pradesh. That is almost two hours of difference in where the sun is. With one clock for everyone, the difference shows up in sunrise and sunset times:
| Place | Longitude | 21 Junesunrise / sunset | 21 Decembersunrise / sunset |
|---|---|---|---|
| Dong, Arunachal Pradesh | 97.0°E | 4:05 AM / 6:01 PM | 5:49 AM / 4:10 PM |
| Kolkata | 88.4°E | 4:52 AM / 6:23 PM | 6:11 AM / 4:56 PM |
| Delhi | 77.2°E | 5:23 AM / 7:21 PM | 7:09 AM / 5:28 PM |
| Mumbai | 72.9°E | 6:01 AM / 7:18 PM | 7:06 AM / 6:05 PM |
| Dwarka, Gujarat | 69.0°E | 6:10 AM / 7:40 PM | 7:28 AM / 6:15 PM |
Sunrise and sunset in IST, calculated for 2026. The same clock time means very different daylight at each end of the country.
In the Northeast, it is fully light by 5 AM in summer and dark soon after 4 PM in winter, while offices, schools and railways keep hours set for the rest of the country. Critics argue that this wastes daylight hours and electricity, and affects sleep.
“Tea garden time” and the IST-II proposal
Assam’s tea gardens have long set their clocks an hour ahead of IST, an informal arrangement known as chai bagan (tea garden) time, so that work starts with the early daylight.
In 2018 scientists at CSIR-NPL, the laboratory that maintains IST, published a study arguing that two time zones would be practical: IST-I at UTC+5:30 for most of the country, and IST-II at UTC+6:30 for Assam, Meghalaya, Nagaland, Arunachal Pradesh, Manipur, Mizoram, Tripura and the Andaman and Nicobar Islands. They proposed drawing the line at the border between West Bengal and Assam, which the railways could handle. The central government has not adopted it. Arguments for keeping one zone include simpler railway and flight timetables, banking and broadcasting, and national unity.
What it means when you work with India
Because India never changes its clocks, the gap to countries that do use daylight saving time changes twice a year, on their dates, not India’s. This catches people out every March and November.
| India compared with | Their winter | Their summer |
|---|---|---|
| New York | 10 h 30 min behind | 9 h 30 min behind |
| London | 5 h 30 min behind | 4 h 30 min behind |
| Los Angeles | 13 h 30 min behind | 12 h 30 min behind |
| Dubai | 1 h 30 min behind, all year | |
| Singapore | 2 h 30 min ahead, all year | |
| Sydney | 5 h 30 min ahead (their summer) | 4 h 30 min ahead (their winter) |
A US client who calls at 9:00 AM New York time reaches India at 7:30 PM in winter, but 6:30 PM in summer. For UK teams, the working-day overlap with India grows by an hour in summer. The converter pages for IST to EST, IST to GMT and IST to PST show both seasons.
Frequently asked questions
How many time zones does India have?
One. The whole country uses Indian Standard Time, UTC+5:30, all year.
Why is IST 5 hours 30 minutes ahead of UTC?
IST is based on the 82°30′E meridian near Mirzapur. Each hour equals 15 degrees of longitude, and 82.5 divided by 15 is 5.5 hours.
Does India use daylight saving time?
No. India does not change its clocks, so the gap to the US, UK and Europe changes when those countries change theirs.
Will the Northeast get its own time zone?
A 2018 CSIR-NPL study proposed IST-II at UTC+6:30 for the Northeast and the Andaman and Nicobar Islands, but the government has not adopted it. Assam’s tea gardens unofficially run an hour ahead.
Sources
- Britannica – Indian time zone
- Wikipedia – Indian Standard Time; Calcutta Time; Bombay Time
- CSIR-NPL – Necessity of two time zones: IST-I (UTC+5:30) and IST-II (UTC+6:30) in India (2018)
- Research Matters – A case for two time zones in India
Checked on 30 September 2026. Times on this page are worked out with the IANA time zone database; live clocks use your browser’s copy of it.