The biggest and smallest daylight saving shifts
Australia/Lord_Howe moves its clocks by 30 minutes rather than the usual hour, and it is the only zone on Earth that does. At the other extreme, Antarctica/Troll moves by 2 hours.
Every size of daylight saving shift in use
| # | Size of the shift | Zones doing it | Which zones |
|---|---|---|---|
| 1 | 2 hours | 1 | Antarctica/Troll |
| 2 | 1 hour | 129 | Africa/Cairo, Africa/Casablanca, Africa/Ceuta and 126 more |
| 3 | 30 minutes | 1 | Australia/Lord_Howe |
How the size of a shift was measured
For each zone we collected every offset it uses across 2026, by reading its offset at the start of the year and at each transition, then subtracted the smallest from the largest. For a zone that moves once forward in spring and once back in autumn, that difference is the size of the daylight saving shift. For a zone that does not move at all, it is zero and the zone is excluded.
The method has one honest limitation worth naming. A zone that permanently changed its standard offset during 2026, rather than moving seasonally, would also show two offsets and would appear here as if it observed daylight saving. That is rare, it happens perhaps once every few years somewhere in the world, and the alternative, parsing rule text, introduces more failure modes than it removes.
The count covers all 419 zone identifiers we publish, which is the complete inhabited world rather than a sample of it. No city catalogue is involved, so unlike most pages here there is no population floor to caveat. Every zone that changes its clocks is counted, including the ones whose entire population is a research station.
The half hour shift, kept by one island
Australia/Lord_Howe is the only zone in the world that moves its clocks by 30 minutes. Lord Howe Island sits in the Tasman Sea with a permanent population of a few hundred people, keeps UTC+10:30 in winter and UTC+11 in summer, and therefore aligns with Sydney for half the year and sits half an hour ahead of it for the other half. The arrangement dates from 1981, when the island tried a full hour and decided it was too much.
It is a small fact with a disproportionate footprint in software, because it is the only real-world counterexample to the assumption that daylight saving means "add one hour". Any code that applies a fixed hour when a zone enters summer time is wrong for Lord Howe Island, and there is no other place on Earth that will catch the bug.
The two hour shift, kept by a research station
Antarctica/Troll moves by 2 hours, twice the normal amount, and it is the only zone that does. Troll Station in Queen Maud Land spends the Antarctic winter on UTC and the summer on UTC+2, which sounds arbitrary until you know that the station is supplied by flights from South Africa and that matching Central European Summer Time for the season makes those flights and the research schedule workable. Antarctica has no indigenous time zones, so each station simply picks the clock its supply chain runs on.
Between those two extremes, 129 zones move by exactly one hour, which is the overwhelming norm and the reason the two exceptions are worth knowing. The question of when they move, rather than by how much, is covered on the next clock change page, and the question of who bothers at all on the no daylight saving page.
Questions about this ranking
- Does daylight saving always mean one hour?
- Almost always, but not quite. 129 zones move by an hour, Australia/Lord_Howe moves by 30 minutes, and Antarctica/Troll moves by 2 hours.
- Which time zone has a 30 minute daylight saving shift?
- Australia/Lord_Howe, covering Lord Howe Island in the Tasman Sea. It is the only one in the world, and it has worked that way since 1981.
- Why does an Antarctic station change its clocks by two hours?
- Because Troll Station's flights and supply chain run from Europe and South Africa. Sitting on UTC in winter and UTC+2 in summer keeps the station aligned with the schedule it depends on.
- How many zones change their clocks at all?
- 131 of the 419 we publish, in 2026. The large majority of the world's zones never move.