Why New York and London are 4 hours apart every March

Most of the year, the maths is simple: New York plus five hours gives you London. Then one March morning your recurring call lands an hour earlier than usual, and nobody quite knows why. The reason is that the two countries change their clocks on different days.

How far apart are New York and London normally?

For most of the year the answer is a clean 5 hours, with London ahead. New York runs on Eastern Time and London on UK time, and the two offsets stay locked together because both regions observe daylight saving. When both have shifted their clocks, the five-hour gap is restored. The problem is the in-between weeks, when only one side has moved.

Why does the gap drop to 4 hours?

Both countries put their clocks forward in spring, but not on the same date. The US moves first, on the second Sunday of March. The UK and the rest of the EU wait until the last Sunday of March. For the weeks in between, the US has lost an hour and the UK has not, so New York creeps one hour closer to London. Five hours becomes four.

Once the UK springs forward too, both sides have shifted by the same amount and the familiar 5-hour gap snaps back into place.

What are the exact 2026 dates?

Here is the spring sequence for 2026. The misaligned window is the stretch where only one country has changed its clocks.

It happens in reverse each autumn, too. The UK falls back on the last Sunday of October (25 October 2026), but the US does not fall back until the first Sunday of November (1 November 2026). For that one week, 25 October to 1 November, the gap is again 4 hours rather than 5.

Why don't the US and UK change on the same day?

There is no shared rule. The United States fixed its spring-forward date to the second Sunday of March in 2007. The UK and EU follow a separate convention: the last Sunday of March and the last Sunday of October. Because the two calendars were designed independently, their dates simply do not line up, and the result is two short windows each year where the offset is off by an hour.

How do I stop getting caught out?

The safest habit is to read each person's actual local time rather than add or subtract a fixed number. A tool that knows the real rules will show New York at 1:00 PM London during the March window and 2:00 PM the rest of the year, without you having to remember which week you are in. That is exactly what Atlas does: pin New York and London on the map, and it accounts for every clock change on both sides automatically.