Last week was one of them. Europe set its clocks back on October 25, 2026 and the US followed on November 1, so for seven days New York was 4 hours behind London instead of 5. Recurring calls slipped by an hour for someone. Here are the dates for 2027, what the gap weeks do to call times, and the habits that stop a missed call.
When do the US and Europe change clocks?
The rules are fixed, but they use different Sundays:
| Rule | 2026 | 2027 | |
|---|---|---|---|
| US, forward | Second Sunday of March | March 8 | March 14 |
| UK and EU, forward | Last Sunday of March | March 29 | March 28 |
| UK and EU, back | Last Sunday of October | October 25 | October 31 |
| US, back | First Sunday of November | November 1 | November 7 |
The US rule comes from NIST: forward at 2 a.m. local time on the second Sunday of March, back at 2 a.m. on the first Sunday of November. The UK changes on the last Sundays of March and October, according to GOV.UK, and the tz database’s europe file records the same EU rule. Across the EU and the UK, every country switches at the same moment, 1 a.m. UTC, so London, Berlin and Athens change together. In the US, each zone switches at 2 a.m. its own time.
Arizona (except the Navajo Nation) and Hawaii do not change clocks, according to NIST. For a Phoenix client, only the European change moves your call times.
Which weeks are out of step in 2027?
Two periods:
| Gap period | What is different | New York to London |
|---|---|---|
| March 14 to 27, 2027 (two weeks) | The US is on summer time; Europe is not yet | 4 hours instead of 5 |
| October 31 to November 6, 2027 (one week) | Europe is back on winter time; the US is not yet | 4 hours instead of 5 |
Outside those weeks, both sides are on the same kind of time and the usual gaps apply.
What time is it in Europe when it is 9 a.m. in New York?
| City | Usual | In the gap weeks |
|---|---|---|
| London (UK) | 2 p.m. | 1 p.m. |
| Lisbon (Portugal) | 2 p.m. | 1 p.m. |
| Berlin, Paris, Madrid, Rome | 3 p.m. | 2 p.m. |
| Athens, Helsinki, Bucharest | 4 p.m. | 3 p.m. |
And for the West Coast, when it is 9 a.m. in Los Angeles:
| City | Usual | In the gap weeks |
|---|---|---|
| London, Lisbon | 5 p.m. | 4 p.m. |
| Berlin, Paris, Madrid, Rome | 6 p.m. | 5 p.m. |
| Athens, Helsinki, Bucharest | 7 p.m. | 6 p.m. |
In the gap weeks the US day starts an hour earlier in your day. That is useful from Athens, where New York’s morning normally starts at 4 p.m., and a trap from London, where a 1 p.m. call can land in your lunch hour.
What happens to recurring meetings?
A calendar invite is fixed to the organizer’s time zone. Everyone else sees it converted to their own zone, so when only one side has changed clocks, the meeting moves for the other side.
A made-up example: a New York client sends a weekly invite for Tuesdays at 10 a.m. Eastern to a designer in Berlin.
| Week | New York | Berlin |
|---|---|---|
| Most of the year | 10 a.m. | 4 p.m. |
| March 16 or November 2, 2027 (gap weeks) | 10 a.m. | 3 p.m. |
If the designer had sent the invite instead, for 4 p.m. Berlin time, the client would see 11 a.m. in those weeks. Neither calendar is wrong. The meeting stays put for whoever created it.
What about countries that don’t change clocks?
India, Pakistan, the UAE, Nigeria and the Philippines keep the same time all year. For calls with the US, the European dates do not matter; only the US dates do. From November 7, 2027 to March 2028, US business hours arrive one hour later in your day:
| You are in | 9 a.m. in New York, US summer (to November 6, 2027) | 9 a.m. in New York, US winter (from November 7, 2027) |
|---|---|---|
| Nigeria | 2 p.m. | 3 p.m. |
| UAE | 5 p.m. | 6 p.m. |
| Pakistan | 6 p.m. | 7 p.m. |
| India | 6:30 p.m. | 7:30 p.m. |
| Philippines | 9 p.m. | 10 p.m. |
Our country guides have the full call windows: India, Pakistan and Nigeria.
How do you keep calls on time in the gap weeks?
- Put the gap weeks in your calendar now. Add a reminder on March 12 and October 29, 2027, the Fridays before each period starts.
- Write both zones in every invite and email. “Tuesday, 10 a.m. ET / 3 p.m. Berlin” leaves nobody guessing.
- Use city names or “Eastern”, not EST or EDT. EST is New York’s winter time only. “Eastern” and “New York time” are right all year.
- Know whose zone the invite is in. If the client organizes, your side moves. If you organize, theirs does.
- Confirm the day before. A one-line email in the gap weeks, “Still on for 3 p.m. my time, 10 a.m. yours?”, catches the slip.
- Check your voicemail greeting. If it gives hours in your local time, it is an hour off for US callers in these weeks. Giving hours in Eastern time avoids that.
The US time-zone clock shows the current time in each US zone, and the best time to call US clients has call windows for more countries.
How does a US number help when times slip?
Some calls will still land at the wrong hour. A US number with voicemail means a client who calls an hour early leaves a message instead of hearing nothing. On the TripoSIM US Virtual Number, incoming calls are included with a fair use of 300 minutes a month, and voicemail messages can be up to 2 minutes, up to 30 a month, kept 30 days. TripoSIM says calls ring even when the app is closed once notifications and the microphone are allowed; a phone that is off, offline or has notifications blocked does not ring, and callers reach voicemail.
When you call back, 300 outgoing minutes a month to US and Canadian numbers are included. The number receives texts but cannot send them, so for a quick “running late” note, email works. Our voicemail greeting scripts show how to state hours in a US time zone.
The bottom line
In 2027 the US changes clocks on March 14 and November 7, and the UK and EU on March 28 and October 31. From March 14 to 27 and from October 31 to November 6, New York is one hour closer to Europe: 9 a.m. in New York is 1 p.m. in London and 2 p.m. in Berlin. Mark those weeks, write both zones in every invite, and confirm calls the day before. If you work from a country that does not change clocks, only the US dates matter.