Half-hour and quarter-hour time zones
Not rounding errors, not bugs — the legal time of about a fifth of the world's population, and the fastest way to find out whether a converter is any good.
The short answer
Several countries sit at half-hour or quarter-hour offsets. India is UTC+5:30, Nepal UTC+5:45, Iran UTC+3:30, Myanmar UTC+6:30.
These are not approximations. They are the legal civil time of those countries, and any tool that rounds them is simply wrong.
The list
| Offset | Where |
|---|---|
| UTC−3:30 | Newfoundland, Canada |
| UTC+3:30 | Iran |
| UTC+4:30 | Afghanistan |
| UTC+5:30 | India, Sri Lanka |
| UTC+5:45 | Nepal |
| UTC+6:30 | Myanmar, Cocos Islands |
| UTC+8:45 | Eucla, Western Australia |
| UTC+9:30 | South Australia, Northern Territory |
| UTC+10:30 | Lord Howe Island (summer) |
| UTC+12:45 / +13:45 | Chatham Islands, New Zealand |
India alone accounts for well over a billion people. This is not an edge case by population — it is an edge case only in the sense that software written in whole-hour zones tends to forget it.
Why they exist
A national compromise. India spans enough longitude for two zones. Rather than split the country, it chose a single offset midway between them — hence the half hour. Iran, Afghanistan and Myanmar made similar single-zone compromises.
Geographic accuracy. Newfoundland's half hour genuinely reflects its longitude, which sits between the standard hourly meridians.
Deliberate distinction. Nepal's 45 minutes is set to the meridian of Mount Gaurishankar, and is understood partly as an assertion of independence from Indian Standard Time next door — a 15-minute difference that is entirely intentional.
Chatham Islands keep a 45-minute offset from mainland New Zealand, which means they also carry a 45-minute daylight saving variant — UTC+13:45 and UTC+12:45.
What they break
Whole-hour arithmetic. Any conversion done by adding integers is 30 or 45 minutes out. A meeting scheduled that way lands in the wrong half of an hour.
Naive UI. Time zone pickers offering only whole-hour offsets cannot represent India. Some genuinely do not.
Assumptions about day boundaries. With a 45-minute offset, midnight in one place is 00:45 or 23:15 in another, so day-boundary calculations that assume alignment fail.
Overlap calculations. Working out shared hours between Kathmandu and anywhere requires minute-level scanning, not hour-level.
The one to test with
If you want to know whether a scheduling tool is trustworthy, convert 10am IST to EST.
The correct answer is not one number: India is 10:30 hours ahead of New York in winter and 9:30 hours ahead in summer, because India does not observe daylight saving and the US does. A tool that gives one fixed answer, or rounds to a whole hour, has failed on both counts.
Related: Why is India 30 minutes off? · Nepal is 45 minutes off · IST to EST
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Figures on this page are computed from the IANA time zone database. Last generated 2026-08-18.