Time zones explained
Half-hour and 45-minute time zones
Every time zone that isn't a whole hour from UTC: India, Nepal, Iran, Afghanistan, Myanmar, Newfoundland, central Australia and the Chatham Islands.
By Shahid Shaikh · Updated
Most of the world is a whole number of hours from UTC. A handful of places aren’t, and they’re exactly where mental time-zone maths goes wrong. I live in one of them (Mumbai, UTC+5:30), which is why Time Zone Pro treats odd offsets as normal from the start.
Every non-hourly time zone
| Place | January | July | Notes |
|---|---|---|---|
| India | UTC+5:30 | UTC+5:30 | The most populous half-hour zone: about 1.4 billion people on UTC+5:30. |
| Sri Lanka | UTC+5:30 | UTC+5:30 | Shares India's offset. |
| Nepal | UTC+5:45 | UTC+5:45 | One of only two 45-minute offsets in use. |
| Iran | UTC+3:30 | UTC+3:30 | Stopped observing daylight saving time in 2022. |
| Afghanistan | UTC+4:30 | UTC+4:30 | No daylight saving time. |
| Myanmar | UTC+6:30 | UTC+6:30 | Also used by the Cocos (Keeling) Islands. |
| Newfoundland, Canada | UTC−3:30 | UTC−2:30 | The only half-hour zone in the Americas, with daylight saving. |
| Northern Territory, Australia | UTC+9:30 | UTC+9:30 | Darwin keeps UTC+9:30 all year. |
| South Australia | UTC+10:30 | UTC+9:30 | UTC+9:30 in winter, UTC+10:30 in summer. |
| Marquesas Islands | UTC−9:30 | UTC−9:30 | French Polynesia, UTC−9:30. |
| Chatham Islands, NZ | UTC+13:45 | UTC+12:45 | UTC+12:45, or +13:45 in the southern summer. |
| Eucla, Western Australia | UTC+8:45 | UTC+8:45 | An unofficial UTC+8:45 used by a few hundred people. |
| Lord Howe Island, Australia | UTC+11 | UTC+10:30 | Moves its clocks by only 30 minutes for daylight saving. |
Offsets for 2026, generated from the IANA time zone database.
Why these zones exist
Time zones follow politics as much as geography. India chose one zone for the whole country at the midpoint of its width. Nepal set its clocks to the meridian of Mount Gauri Shankar, 15 minutes ahead of India. Newfoundland kept its own local time when it joined Canada. Each choice makes sense locally and makes scheduling harder for everyone else.
Scheduling with half-hour zones
The common mistake is rounding: thinking of India as “10 hours ahead of New York” when it’s 9½ or 10½ depending on the season. Half an hour is the difference between joining on time and joining to an empty call. Useful pages: EST to IST, PST to IST, UK to IST and AEST to IST.
Frequently asked questions
Why is India's time zone UTC+5:30?
India uses a single time zone for the whole country, centred on 82.5° E longitude near Mirzapur. That meridian sits exactly 5 hours 30 minutes ahead of Greenwich, so India Standard Time is UTC+5:30 all year.
Which countries use a 45-minute offset?
Nepal (UTC+5:45) and New Zealand's Chatham Islands (UTC+12:45, or +13:45 in summer). An unofficial UTC+8:45 is also used around Eucla in Western Australia.
How do I convert to a half-hour time zone?
Add or subtract the full offset including the minutes. 9:00 AM in London (UTC+0) is 2:30 PM in India (UTC+5:30) and 2:45 PM in Nepal (UTC+5:45). Apps that use the IANA time zone database, like Time Zone Pro, do this automatically.