The world's strangest time zones
Time zones are not a tidy grid of whole hours. Right now 15 zones sit at a half or quarter hour offset, the planet spans 25 hours from end to end rather than 24, and 12 zones run their daylight saving in what the northern hemisphere calls winter. Every figure here is read live from the timezone database.
Offsets that are not whole hours
| place | zone | offset now |
|---|---|---|
| Marquesas | Pacific/Marquesas | UTC−09:30 |
| St Johns | America/St_Johns | UTC−02:30 |
| Tehran | Asia/Tehran | UTC+03:30 |
| Kabul | Asia/Kabul | UTC+04:30 |
| Calcutta | Asia/Calcutta | UTC+05:30 |
| Colombo | Asia/Colombo | UTC+05:30 |
| Katmandu | Asia/Katmandu | UTC+05:45 |
| Rangoon | Asia/Rangoon | UTC+06:30 |
| Cocos | Indian/Cocos | UTC+06:30 |
| Eucla | Australia/Eucla | UTC+08:45 |
| Adelaide | Australia/Adelaide | UTC+09:30 |
| Broken Hill | Australia/Broken_Hill | UTC+09:30 |
| Darwin | Australia/Darwin | UTC+09:30 |
| Lord Howe | Australia/Lord_Howe | UTC+10:30 |
| Chatham | Pacific/Chatham | UTC+12:45 |
Amber marks the quarter-hour offsets, the rarest kind.
Why the map refuses to be tidy
The neat picture of 24 slices, each an hour wide, is a diagram rather than a description. Zones follow borders, rivers, politics and habit, and the result is a system with genuinely strange corners.
Start with the width of the world. From Kiritimati at UTC+14:00 to Midway at UTC−11:00 is 25 hours, not 24. The extra comes from islands that chose to sit on the far side of the date line from their neighbours, so for part of every day there are three different calendar dates in use on Earth at once.
Then the fractional offsets. India runs half an hour off the grid so that one zone can serve a country spanning almost 30 degrees of longitude. Nepal went further and sits 45 minutes off, partly to be distinct from India and partly to sit closer to solar noon in Kathmandu. Those quarter-hour zones are the ones that quietly break software: code that assumes offsets are whole hours works everywhere until someone in Kathmandu or the Chatham Islands opens it.
Daylight saving adds its own mess. The dates are not shared, so for a few weeks each spring and autumn the gap between two cities is different from what both parties expect. The southern hemisphere runs its summer time during the northern winter, which means 12 zones move in the opposite direction to Europe and North America. And Lord Howe Island, off Australia, shifts by half an hour rather than a full one, purely because a whole hour was felt to be too much.
None of this is written down on this page. Every number above is read from the IANA timezone database at build time, which is the same source your operating system uses, so when a country changes its rules this page changes with it. That is deliberate: lists of timezone trivia elsewhere on the web are usually years out of date, still listing zones that no longer exist.
If you write software that touches time, the practical lesson is short. Never store an offset, store the zone name. Never assume an offset is a whole number of hours. Never assume the difference between two cities is stable across the year. The full zone reference lists every identifier with its January and July offsets so the exceptions are visible rather than surprising.
FAQ
Why are some time zones offset by 45 minutes?
Nepal, the Chatham Islands and a few others chose offsets that are neither whole nor half hours, usually to sit closer to their true solar time than a neighbour's zone would allow. There are 3 such zones today.
How far apart can two places be?
25 hours. Kiritimati at UTC+14:00 is the furthest ahead and Midway at UTC−11:00 the furthest behind, which is more than a full day and means the two are on different calendar dates for part of every day.
Does everywhere change the clocks by an hour?
No. 2 zones shift by something other than a full hour, Lord Howe Island being the classic case with a half-hour change.