Daylight saving, explained
About a third of the world moves its clocks twice a year, on dates each region picks for itself. That mismatch, not the change itself, is what breaks meetings.
What actually happens
In spring, a region skips an hour: clocks jump from 02:00 to 03:00 and the offset moves one hour further from UTC. In autumn it repeats an hour and the offset moves back. Nothing happens to UTC itself, which is why UTC is the sane thing to store.
The dates do not line up
Europe changes on the last Sunday in March and October. North America changes on the second Sunday in March and the first in November. For about 3 weeks a year the gap between Berlin and New York is five hours rather than six — and for those weeks a recurring 15:00 Berlin call lands an hour earlier for everyone in New York.
| Region | Clocks forward | Clocks back |
|---|---|---|
| European Union | Sun 29 Mar 2026, 02:00 → 03:00 | Sun 25 Oct 2026, 03:00 → 02:00 |
| United Kingdom | Sun 29 Mar 2026, 01:00 → 02:00 | Sun 25 Oct 2026, 02:00 → 01:00 |
| United States & Canada | Sun 8 Mar 2026, 02:00 → 03:00 | Sun 1 Nov 2026, 02:00 → 01:00 |
| Australia (SE states) | Sun 4 Oct 2026, 02:00 → 03:00 | Sun 5 Apr 2026, 03:00 → 02:00 |
| New Zealand | Sun 27 Sep 2026, 02:00 → 03:00 | Sun 5 Apr 2026, 03:00 → 02:00 |
| Brazil, India, Japan, China | No change | No change |
The southern hemisphere runs the other way
Sydney gains its extra hour in October and gives it back in April, so through the northern summer the gap to Europe narrows rather than widens. Countries near the equator mostly never change at all: India, China, Japan and Brazil hold one offset all year.
Hours that do not exist, and hours that happen twice
On a spring-forward morning, 02:30 local never occurs; on an autumn morning it occurs twice. Calendars disagree about what to do with a meeting booked in either. This site refuses to show a non-existent local time and labels the affected day rather than picking one reading and hoping — step the planner onto a changeover date and it says so above the grid.
Recurring meetings are the real hazard. A weekly slot pinned to one participant’s local time will drift for everyone else at least twice a year. Agree whose clock the series belongs to when you set it up.