Why your recurring meeting just moved an hour

Because the difference is not a property of the two places, it is a property of the two places on a date. Each region decides for itself whether to move its clocks and on which day, and no two of those decisions have to agree.

The United States and the European Union both observe daylight saving, both move on a Sunday, and both move by one hour. They do it on different Sundays. For three weeks in spring and one week in autumn, the usual difference between a US city and a European one is an hour out, and every meeting scheduled by offset rather than by local time lands in the wrong place.

On these dates, read from the pinned IANA release rather than typed out here, so they move in the same change as the data the rest of the site computes with.

The rules behind the dates have not changed since 2007. In the United States, daylight saving runs from the second Sunday in March to the first Sunday in November. In the European Union and the United Kingdom it runs from the last Sunday in March to the last Sunday in October, both at 01:00 GMT. Because March has a different number of Sundays each year, the gap between the American and European changeover is two weeks in some years and three in others.

These ones. The table below lists every stretch across 2026 and 2027 over which the difference between New York and Berlin holds, so the short runs are the weeks when the usual six hours is five.

The same table for any other pair

Anchor it to one place's local time, name that place in the invitation, and let the other readings move. A series anchored to nothing drifts for everyone; a series anchored to Berlin is at the same Berlin hour all year and moves once for New York, which is a change one sentence can explain. The scheduling guide covers how to write that sentence.

Then put both changeover dates for the coming year in the series description. It costs one line and removes the twice-yearly message asking whether the meeting moved.