TimezoneSearch

The weeks when the US and Europe are an hour closer

8 min readdstmeetings

A standing call between New York and London does not break on the morning the clocks change. It breaks a few weeks later, when the gap goes back to normal and someone joins at the hour they just spent three weeks using.

The United States and Canada move on the second Sunday of March and the first Sunday of November. The UK and the EU move on the last Sunday of March and the last Sunday of October. US daylight time starts earlier and ends later, so it covers the whole European daylight period. In the shoulders, only North America has changed. Clocks are an hour closer, not an hour further. There is no week when New York and London are six hours apart. They are five hours for most of the year and four hours in those two shoulders. The spring shoulder is the long one, about three weeks. The autumn shoulder is about a week, which is why it gets missed.

What the closer hour does to a real invite

The event has its own time zone. That zone keeps its local hour. Everyone else moves.

Take 4:00 PM in London, which is 11:00 AM in New York at the usual five-hour gap. During a shoulder the gap is four hours, so the same London hour is noon in New York. London did not get pushed later. New York got an easier slot. If the event was created as 11:00 AM in New York, London sees 3:00 PM instead of 4:00 PM during the shoulder. London’s day got easier too.

The nasty moment is the return. On the last Sunday of March, Europe springs forward and the five-hour gap comes back. A London-anchored 4:00 PM, which New York has been attending at noon, is 11:00 AM in New York again. People who kept the shoulder hour in their heads show up an hour late, to a meeting that already happened. The same trap sits on the first Sunday of November, when the US falls back and the autumn shoulder ends. Write the new hour down. Do not trust the habit you built during the short period.

London and New York is the five-to-four case. Berlin and New York and New York and Paris are six hours normally and five in the shoulders. The direction is the same: the shoulder makes the clocks closer, and the non-anchor city’s civil time moves by an hour. Chicago and London is the six-to-five version one zone further west. London and Toronto follows the US dates on the Canadian side, so it has the same shoulders as London and New York.

The west coast shoulders are the good weeks

London and San Francisco are eight hours apart for most of the year, which leaves a thin overlap at the end of London’s day. In the shoulders the gap is seven hours. 9:00 AM in San Francisco is 4:00 PM in London instead of 5:00 PM. That extra hour is the difference between a tolerable weekly call and a call London starts to skip.

Berlin and San Francisco are worse. Nine hours is one lonely slot at Berlin’s exit. Eight hours, which you only get in the shoulders, is the first setting that looks like a meeting. Do not rebuild the quarter around those weeks. When the nine-hour gap returns, go back to a written handoff. The shoulder is a bonus, not the new normal.

What to send the week before

A message that says “daylight saving is this weekend” does not tell anyone what time the call is. Send the series list instead, the Monday before each of the four Sundays, with both local times for the shoulder and both local times for the week after it.

Four lines is enough:

  1. The meeting name and which city’s zone owns the invite. If you do not know, open the event. Clicking a slot on your own calendar anchored it to you, which was a decision even if nobody discussed it. The invite ownership guide is the longer version of that choice.
  2. The local time on each side this week.
  3. The local time on each side next week, after the switch you are approaching.
  4. Who is expected to attend live, and who gets the notes.

Then look at the pair page for that corridor. The schedule there is computed for the current year, so you do not have to translate “second Sunday of March” into a date by hand.

The country-by-country rules, including why the UK still moves with Europe, are in daylight saving time rules by country. The Sunday-night checklist for on-call rotations and jobs that run on local time is separate: the week the clocks change.

One limit of all of this: the shoulder logic above is for North America against the UK and the EU, because US daylight time contains European daylight time. It is not the pattern for Sydney, Cairo, or anywhere else that moves on its own calendar. Those pairs can get further apart, not closer. Use their pages, not this article’s hours.