GMT to EST Converter

What this does

Enter a time in Greenwich Mean Time and read it on the US East Coast clock. The source side is deliberately a fixed zero-offset zone (Etc/GMT) that never observes daylight saving, and the target is America/New_York, which does. So Eastern comes out five hours behind GMT in winter and four hours behind in summer, and the page works out which applies from the date you enter. Nothing leaves your browser, and it keeps converting with the connection off.

Does "GMT" mean the same thing as London time?

Only for half the year, and this is the trap that catches most people booking calls with the UK. GMT is a fixed reference at UTC+0. The London clock sits on GMT from the last Sunday in October to the last Sunday in March, then moves to British Summer Time, BST, which is UTC+1. So a 9:00 AM meeting in London in July is 08:00 GMT, not 09:00 GMT. If your time came off a British colleague's calendar in summer, subtract an hour before typing it here — or open the timezone converter and pick Europe/London, which tracks BST for you.

What is 9am GMT in EST?

4:00 AM Eastern in winter, 5:00 AM in summer. A London working day maps across like this:

The practical overlap is narrow: roughly 14:00–17:30 GMT, which is 9:00 AM–12:30 PM in New York.

How do I convert a GMT time here?

The left-hand field takes the GMT reading:

1. Enter the calendar date along with the time. Only the Eastern side moves with the seasons, so the date is what decides between a five and a four hour drop.
2. Type the GMT clock reading on the left, or press Use now to load the current GMT time.
3. Read the Eastern result on the right; the note underneath spells out how far behind the target zone is at that moment.

Why is London sometimes only four hours ahead of New York?

Because the two countries change clocks on different dates. The US springs forward on the second Sunday in March and falls back on the first Sunday in November; the UK switches on the last Sundays of March and October. For the two or three weeks in March, and the week or so around the end of October, the US is on summer time while Britain is still on GMT, and the London–New York gap narrows from its usual five hours to four.

Is GMT the same as UTC?

For clock arithmetic, yes — both are zero offset and every conversion on this page would be identical under either name. The distinction is historical: GMT is an astronomical standard tied to the Greenwich meridian, UTC an atomic one kept within a second of it. If your time came from a server or a timestamp rather than a British calendar, use UTC to EST instead.