Four or five hours, depending on the season
GMT never changes, but Eastern Time does. In winter, on EST, GMT is 5 hours ahead. In summer, on EDT, the gap shrinks to 4 hours. Right now Eastern Time is on EDT, so the gap is 4 hours.
Some winter examples, on EST:
- 7:00 AM EST is 12:00 PM (noon) GMT.
- 12:00 PM (noon) EST is 5:00 PM GMT.
- 7:00 PM EST is 12:00 AM (midnight) GMT, the next day.
- In summer add 4 hours instead: 12:00 PM EDT is 4:00 PM GMT.
GMT, UTC and BST
GMT and UTC show the same time for everyday purposes. UTC, Coordinated Universal Time, is the atomic time standard the world sets its clocks by. GMT is the time zone at zero hours from it, and the two never differ by more than a second.
London is not on GMT all year. From the last Sunday in March to the last Sunday in October the UK uses British Summer Time, BST, which is GMT plus one hour. To convert to London time in summer, use GMT plus one.
When the gap to London is different
The US and the UK change their clocks on different dates. For a few weeks each year, from the second Sunday in March to the last Sunday in March and from the last Sunday in October to the first Sunday in November, New York is only 4 hours behind London instead of 5. This converter uses GMT, which stays fixed, so its result is always exact.
Where you see GMT and UTC times
Flight plans, weather reports, server logs, online events and scientific data often use GMT or UTC so everyone reads the same clock. Pilots call it Zulu time. When a time ends in Z, such as 14:00Z, it means 14:00 GMT.
Questions and answers
How many hours is Eastern Time behind GMT?
Eastern Time is 5 hours behind GMT in winter, on EST, and 4 hours behind in summer, on EDT. Right now the gap is 4 hours.
What is 12 PM EST in GMT?
12:00 PM EST is 5:00 PM GMT. In summer, 12:00 PM EDT is 4:00 PM GMT.
Is GMT the same as UTC?
For everyday use, yes. UTC is the time standard and GMT is the zone that sits at zero hours from it. They never differ by more than a second.
Is London on GMT?
Only in winter. From late March to late October London uses British Summer Time, which is one hour ahead of GMT.
Does GMT change for daylight saving time?
No. GMT stays the same all year. Countries that use it in winter, such as the UK, switch to a different summer time instead.