Convert EST to GMT
Five hours in winter — but the two sides change their clocks on different weekends, so for a few weeks each year the answer is neither five nor four.
The short answer
Add 5 hours. 09:00 EST is 14:00 GMT. 15:00 EST is 20:00 GMT.
That holds while New York is on EST (UTC−5) and the UK is on GMT (UTC+0) — roughly November to March. Outside that, both sides have moved to their summer clocks and the gap is still five hours, but the correct labels are EDT and BST. For about two weeks each year they are out of step and the gap is four hours.
The winter table
| New York (EST) | London (GMT) |
|---|---|
| 05:00 | 10:00 |
| 07:00 | 12:00 |
| 09:00 | 14:00 |
| 12:00 | 17:00 |
| 15:00 | 20:00 |
| 19:00 | 00:00 next day |
Why five hours is usually right
New York on EST is UTC−5. London on GMT is UTC+0. The difference is five hours.
In summer both move forward by an hour — New York to UTC−4, London to UTC+1 — so the gap returns to five. The relationship is stable for most of the year: 5 hours ahead in January, 5 hours ahead in July.
The gap weeks
Here is the part that catches recurring meetings.
The United States and the United Kingdom do not change their clocks on the same dates. The US springs forward on the second Sunday in March. The UK and the EU wait until the last Sunday in March. In autumn the order reverses: Europe falls back in late October, the US in early November.
During those windows one side has moved and the other has not, so the transatlantic gap is four hours instead of five.
Nothing in the calendar entry changes. The invite is identical. It simply happens an hour earlier for half the attendees, for two or three weeks, twice a year — and then fixes itself, which is why nobody ever gets round to investigating it.
Terminology worth getting right
- GMT is a time zone: the UK's winter clock, UTC+0.
- BST is British Summer Time, UTC+1, in effect roughly late March to late October. For those months, "GMT" is not British local time.
- UTC is the underlying standard and never changes. For written timestamps it is the better choice — see UTC to EST.
So "3pm GMT" in July is the same mistake as "3pm EST" in July, in a different country. Both name a winter clock during summer.
The safe way to schedule transatlantic
Write cities: "2pm London / 9am New York." A city name resolves through the time zone database to whatever offset is genuinely in effect on that date, including inside the gap weeks.
If you run a recurring transatlantic call, it is worth checking it in mid-March and late October specifically — those are the only two moments it can silently move.
Related: Eastern Time to GMT · EST vs EDT · UTC to EST
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Figures on this page are computed from the IANA time zone database. Last generated 2026-08-18.