The 5-hour gap that shrinks to 4
A 9:00 AM call from New York lands in London at 2:00 PM. That is the January math. Try the same call in July and London picks up at 1:00 PM. The difference is not GMT shifting (it never does) but Eastern Time jumping between EST (UTC−5) and EDT (UTC−4). The gap is five hours from early November to mid-March. It contracts to four hours the rest of the year. Get the season wrong and you miss the meeting by an hour.
The fixed dates for 2026: clocks spring forward on Sunday 8 March at 02:00 local, and fall back on Sunday 1 November at 02:00 local. Between those dates, Eastern Time runs on EDT. Outside them, EST.
How the converter works
Check the offset before you type
Look at the clock display. If it reads "EST (UTC−5)", add five hours to reach GMT. If it reads "EDT (UTC−4)", add four. Do not guess. The date decides.
Enter the time cleanly
The converter accepts 12-hour and 24-hour formats. "2:00 PM" EST returns 19:00 GMT. "02:00" (2 AM) returns 07:00 GMT. Twelve hours apart. Double-check AM/PM before you hit convert.
Pick the right Eastern Time label
"EST" in the converter means standard time only. Selecting EST for a July date produces a result off by one hour. Match the label to the date.
EST to GMT conversion table
| Eastern Time (EST/EDT) | GMT (winter) | BST (summer) |
|---|---|---|
| 12:00 AM (midnight) | 5:00 AM | 4:00 AM |
| 9:00 AM | 2:00 PM | 1:00 PM |
| 1:00 PM | 6:00 PM | 5:00 PM |
| 2:00 PM | 7:00 PM | 6:00 PM |
| 3:00 PM | 8:00 PM | 7:00 PM |
| 4:00 PM | 9:00 PM | 8:00 PM |
| 5:00 PM | 10:00 PM | 9:00 PM |
| 6:00 PM | 11:00 PM | 10:00 PM |
Read it both ways: 5:00 PM EST is 10:00 PM GMT in January. 5:00 PM EDT is 9:00 PM BST in July.
EDT to BST: the summer shift
Four hours, not five
From the second Sunday of March to the first Sunday of November, Eastern Time runs on EDT (UTC−4). The UK simultaneously moves to British Summer Time (UTC+1). The gap closes to four hours.
9:00 AM EDT equals 1:00 PM BST. 3:00 PM EDT equals 7:00 PM BST.
The one-hour scheduling trap
Someone books a "3:00 PM EST" conference call in June. The London colleague sees 7:00 PM BST. But the organizer meant 3:00 PM EDT, which is 8:00 PM BST. One hour late. This is the most common transatlantic scheduling error. If an invitation says "EST" between March and November, assume the sender meant EDT and verify.
Why GMT stays fixed while EST moves
GMT is mean solar time at the Royal Observatory in Greenwich, London. It does not observe daylight saving. The UK switches to BST in summer, but GMT itself remains locked at UTC+0.
Eastern Time moves because the United States and Canada observe daylight saving. The shift happens at 02:00 local time, chosen to minimise disruption after bars close and before early commuters head out. The EST-to-GMT conversion is stable only from November to March. The rest of the year, convert EDT to BST instead.
Business calls and the narrow overlap
Finding a window that works
Eastern Time and London working hours (9:00 AM to 5:00 PM local) overlap briefly. In winter, a 9:00 AM EST call hits London at 2:00 PM GMT. That works. In summer, 9:00 AM EDT lands at 2:00 PM BST. Also fine. But a 4:00 PM EST meeting in January is 9:00 PM GMT. Too late. Schedule calls before noon Eastern Time.
Financial markets
NYSE and NASDAQ open at 9:30 AM Eastern and close at 4:00 PM Eastern. In winter, that is 2:30 PM to 9:00 PM GMT. In summer, 1:30 PM to 8:00 PM BST. The London, New York forex overlap (8:00 AM to 12:00 PM ET) is the most liquid trading period of the day.
Travel and live events
Flights
Flying New York to London in winter: a 6:00 PM EST departure plus roughly seven hours in the air puts you on the ground around 6:00 AM GMT. In summer, the same departure arrives near 5:00 AM BST. Adjust sleep accordingly.
TV and streaming
US primetime starts at 8:00 PM Eastern. In winter, that is 1:00 AM GMT. In summer, 8:00 PM EDT is midnight BST. Both are late for UK viewers. Recordings and on-demand streaming solve it. The "8/7c" notation means 8 PM Eastern, 7 PM Central.
Servers and code
Scheduling a server restart for 2:00 AM EST in July means 2:00 AM EDT, a different UTC offset. Store times in UTC. Convert to Eastern Time only for display. The IANA zone for Eastern Time is America/New_York. Use it. Do not hardcode offsets.
The rule: when an event labelled "EST" falls between March and November, assume EDT. Check the date against the clock display. Convert. Do not trust memory. One hour is all it takes to miss the call.