Is New York always 5 hours behind London?

No. For most of the year the difference is 5 hours, but for about 2 to 3 weeks in March and about 1 week in late October/early November, the difference is 4 hours.

When exactly does the 4-hour gap happen in spring?

It happens between the second Sunday of March (when the US starts daylight saving) and the last Sunday of March (when the UK starts daylight saving).

When exactly does the 4-hour gap happen in autumn?

It happens between the last Sunday of October (when the UK ends daylight saving) and the first Sunday of November (when the US ends daylight saving).

What time is it in London when it is 9:00 in New York during the 4-hour gap?

When the gap is 4 hours, 9:00 in New York is 13:00 in London.

Time Difference Between London and New York, Month by Month

New York runs 5 hours behind London for most of the year. Then, for a few weeks each spring and autumn, the gap shrinks to 4 hours. This happens because the United States and the United Kingdom switch to summer time on different dates. During the transition periods in March and late October, 9:00 in New York is 13:00 in London. For the other ten months, 9:00 in New York is 14:00 in London.

The Standard Difference Most of the Year

For the majority of the year, New York is 5 hours behind London. London uses Greenwich Mean Time (GMT, UTC+0) in winter and British Summer Time (BST, UTC+1) in summer. New York uses Eastern Standard Time (EST, UTC-5) in winter and Eastern Daylight Time (EDT, UTC-4) in summer. Both cities shift their clocks forward and backward by one hour, so the 5-hour difference holds for roughly 10 months. When scheduling a call or checking a flight, rely on the 5-hour gap for most dates.

When the Gap Becomes 4 Hours Spring Transition

Spring Window

Each March, the United States moves its clocks forward on the second Sunday. The United Kingdom follows later, on the last Sunday of March. Between these two dates, New York is on EDT (UTC-4) while London is still on GMT (UTC+0). That makes the difference 4 hours instead of 5. This period lasts 2 to 3 weeks. During this time, 9:00 in New York is 13:00 in London.

When the Gap Becomes 4 Hours Autumn Transition

Autumn Window

In autumn, the United Kingdom ends summer time on the last Sunday of October, switching back to GMT (UTC+0). The United States ends daylight saving a week later, on the first Sunday of November, moving back to EST (UTC-5). Between the UK end date and the US end date, London is on GMT while New York is still on EDT. This again creates a 4-hour difference. The period lasts about one week. During that week, 9:00 in New York is 13:00 in London.

Month by Month Breakdown

Here is how the time difference between London and New York changes month by month. Exact dates shift each year, but the pattern is consistent.

January and February: Both cities are on standard time (London GMT, New York EST). Difference is 5 hours.
March: For the first part of the month, both are on standard time (5 hours). After the US switches to EDT, but before the UK switches to BST, the difference is 4 hours. After the UK switches, both are on summer time, and the difference returns to 5 hours.
April through September: Both cities are on summer time (London BST, New York EDT). Difference is 5 hours.
October: For most of the month, both are on summer time (5 hours). After the UK switches to GMT, but before the US switches to EST, the difference is 4 hours. After the US switches, both are on standard time, and the difference is 5 hours.
November and December: Both cities are on standard time. Difference is 5 hours.

Scheduling Calls and Meetings

Quick Conversion Rules

Add 5 hours to New York time to get London time for most of the year. A 9:00 start in New York means a 14:00 call in London.

During the 4-hour gap periods in March and late October, add only 4 hours. That same 9:00 New York time becomes 13:00 in London.

Confirm the Dates

Check the exact dates of the US and UK clock changes each year. The US starts on the second Sunday of March and ends on the first Sunday of November. The UK starts on the last Sunday of March and ends on the last Sunday of October. When in doubt, use a world clock tool to confirm the current time difference.

Why the Difference Changes

The time difference between London and New York changes because the two countries do not start and end summer time on the same dates. The United States begins daylight saving on the second Sunday in March and ends it on the first Sunday in November. The United Kingdom begins BST on the last Sunday in March and ends it on the last Sunday in October. This creates two short windows each year when one city has shifted its clock while the other has not. During those windows, the gap is 4 hours instead of the usual 5.