Convert GMT to EST Greenwich Mean Time ↔ Eastern Standard Time Free Online Secure
Type a time in GMT and read it in EST straight away. The offset is −5 h, the arithmetic wraps at midnight, and the answer says which day it lands on.
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Through the day — Convert GMT to EST (Greenwich Mean Time ↔ Eastern Standard Time)
| GMT | EST |
|---|---|
| 00:00 | 19:00 |
| 03:00 | 22:00 |
| 06:00 | 01:00 |
| 09:00 | 04:00 |
| 12:00 | 07:00 |
| 15:00 | 10:00 |
| 18:00 | 13:00 |
| 21:00 | 16:00 |
Where these units come from
Until the middle of the nineteenth century every town kept its own noon, set by the sun overhead, and nobody minded that the next town was four minutes behind. Railways ended that: a timetable cannot be written for a hundred local noons. Britain put its railways on Greenwich time in 1847, and in 1884 the International Meridian Conference in Washington chose Greenwich as the prime meridian and sketched the twenty-four-hour scheme we still use. Greenwich Mean Time was the world's reference until 1972, when Coordinated Universal Time replaced it: UTC is kept by atomic clocks and tied back to the turning Earth by leap seconds. The abbreviations on this page name standard time — the winter setting — which is why each one is a fixed number of hours rather than something that drifts through the year.
Where you meet them
A time zone becomes real the moment two people in different places have to agree on one moment: a call between offices, a flight that lands before it took off, a market that opens while you are asleep, a deadline written in somebody else's afternoon. Server logs, train and flight schedules and anything stamped with a time are kept in UTC precisely so that the question can always be settled, no matter whose clock was on the wall.
Questions people ask
What about summer time?
The offsets here are standard-time offsets, the ones a zone keeps in winter. Where summer time is observed, the same places move one hour further on for part of the year and take a different name: Central European Time becomes Central European Summer Time, Eastern Standard Time becomes Eastern Daylight Time. The switching dates are not the same in every country, and the two hemispheres change in opposite months, so for a date inside a summer-time period add an hour to whichever side observes it.
Why isn't every difference a whole number of hours?
Because offsets are decided by governments, not by geometry. India is half an hour off the hour, at UTC+05:30; Nepal is three quarters, at UTC+05:45; the Chatham Islands are at UTC+12:45. Any of these can be changed by law, and several countries have moved their offset within living memory.
Is the answer exact?
Where both units are defined in terms of one another by whole numbers, yes — the page says so above the figure, and the only rounding is in how many digits are shown. Where the ratio has no finite decimal, the page shows twelve significant digits and says the relation is approximate rather than pretending otherwise.
Does anything I type leave my device?
No. The arithmetic runs in your browser; nothing is uploaded and there is no server to upload it to. Load the page once and it keeps working with the network switched off.
Reading a Greenwich time on a New York clock
You have a time in GMT, perhaps from a British broadcaster, a flight schedule, a server log or a message from a colleague in London, and you need to know what it is on the East Coast of the United States. The answer is that Eastern Standard Time runs five hours behind Greenwich. When you convert GMT to EST, you subtract five hours: 15:00 GMT is 10:00 EST, 09:00 GMT is 04:00 EST, and 03:00 GMT is 22:00 EST on the previous calendar day. The previous-day case is the one that catches people out, because it moves the date as well as the clock.
The sections below show how to convert GMT to EST step by step, set out the rule, give a table you can scan, describe each of the two zones, and explain why the gap shrinks to four hours for a few weeks each spring and autumn. They also cover flights, launches, theatre curtains, broadcasts and the things that go wrong when a message is written in a hurry. The arithmetic happens in your browser and nothing you enter is transmitted anywhere.
How to convert GMT to EST
Subtract five, and watch the date
EST is UTC−5 and GMT is UTC+0, so the conversion takes five hours off the clock. If the GMT hour is five or greater, the result stays on the same day: 11:20 GMT is 06:20 EST. If the GMT hour is below five, add twenty-four hours first and move back a day: 02:10 GMT is 21:10 EST the day before.
Eight readings to anchor your intuition
00:30 GMT is 19:30 EST the previous day. 06:15 GMT is 01:15 EST. 09:00 GMT is 04:00 EST. 12:00 GMT is 07:00 EST. 15:45 GMT is 10:45 EST. 18:00 GMT is 13:00 EST. 21:30 GMT is 16:30 EST. 23:45 GMT is 18:45 EST. Only the first of these crosses a midnight boundary.
A shortcut
Subtract six and add one. To convert GMT to EST quickly in your head, note that five is awkward, it can be easier to take off six hours and put one back. From 18:00, six hours gives 12:00, and adding one gives 13:00.
What GMT means in everyday use
The British winter clock
Greenwich Mean Time is the legal time of the United Kingdom from the last Sunday of October to the last Sunday of March. In 2026 the clocks go forward on 29 March and back on 25 October. In the months between, Britain is on British Summer Time, an hour ahead, and a message that says GMT may really mean the London wall clock.
A scientific and technical label
When you convert GMT to EST for a server, bear in mind that in computing GMT is also used as a plain synonym for the zero-offset reference, UTC. HTTP headers, certificates and many logs carry it. When the context is technical, GMT is a fixed scale that never changes with the seasons, which is exactly how the converter on this page treats it.
What EST means
Standard time on the Eastern Seaboard
Eastern Standard Time is five hours behind UTC and applies in winter in cities such as New York, Boston, Washington, Philadelphia, Atlanta, Miami, Toronto, Montreal and Ottawa. In summer these places move to Eastern Daylight Time, UTC−4. Many speakers say EST all year, but strictly speaking the label is wrong between March and November. A safer abbreviation for general use is ET, which stands for whichever of the two applies.
Places that stay on EST
Panama, Jamaica and the Cayman Islands never change their clocks, so they sit on UTC−5 all year round. So do Colombia, Peru and Ecuador on the mainland. The Mexican state of Quintana Roo, home to Cancún, adopted year-round UTC−5 in 2015. For these locations, “EST” is accurate in July as well as in January, although the gap to London changes with Britain’s clocks.
The five-hour gap and what it does to a working day
Overlap of office hours
A standard office day from 09:00 to 17:00 in London is 04:00 to 12:00 in New York. The workday in New York, from 09:00 to 17:00 EST, is 14:00 to 22:00 in London. The two overlap for only three hours, from 14:00 to 17:00 GMT. Teams that meet across the Atlantic therefore cluster their calls in the British afternoon, which is the American morning.
Early starts and late finishes
Anybody in London who needs to convert GMT to EST for a New York colleague before 14:00 GMT is calling before the American working day begins, and anybody in New York who wants to reach London after noon EST is calling after the British day has ended. A quick convert GMT to EST before sending the invitation settles who bears the inconvenience.
Concorde and the clocks
The supersonic airliner left London at 10:30 and landed in New York at 09:25 local time, because the flight took about three hours and fifty-five minutes and the clock difference was five hours. Passengers famously arrived before they left. The effect on a GMT-to-EST conversion is exactly the same as it was then.
When the gap becomes four hours
Two calendars, two sets of dates
The United States starts daylight saving time on the second Sunday of March and ends it on the first Sunday of November. Britain and the rest of Europe start on the last Sunday of March and end on the last Sunday of October. In 2026 the American dates are 8 March and 1 November, and the European dates are 29 March and 25 October.
The mismatched weeks
From 8 March until 28 March, New York is on EDT (UTC−4) while London is still on GMT, so the gap is four hours. From 25 October until 31 October, London is back on GMT while New York remains on EDT, so again the gap is four hours. In total there are four such weeks in a year. Everywhere else the gap is five hours, either GMT to EST in winter or BST to EDT in summer.
What the converter shows
The calculator above applies the standard five-hour winter difference. If the date falls inside one of the mismatched weeks, remember that a conversion from GMT lands on EDT, so 14:00 GMT is 10:00 on a New York clock rather than 09:00.
Spaceflight from the Eastern coast
Launch times in two clocks
Rocket launches from Florida are announced in Eastern time. A launch window opening at 10:15 EST is 15:15 GMT. A night launch at 23:40 EST is 04:40 GMT the following morning. Followers in Europe who set an alarm by the GMT figure can still be late if the date has moved, so it helps to check the day as well as the hour.
A habit from the control room
Mission teams quote countdown clocks in mission elapsed time and communicate with the world in UTC. If you read “T-minus” in a live commentary and a UTC time in a press note, a “convert GMT to EST” calculation on the UTC number gives you the local view in Florida.
Broadway and the London stage
Curtain times
An evening performance on Broadway usually begins at 19:00 or 20:00 local time, which is 00:00 or 01:00 GMT on the next date. A matinee at 14:00 EST starts at 19:00 GMT. Anyone in London who wants to watch a live stream of a Broadway show therefore watches either late at night or in the early evening.
The reverse direction
A West End matinee at 14:30 London time is 09:30 in New York in winter. An evening performance at 19:30 in London is 14:30 in New York. If you buy a ticket for a streamed performance, check which clock the listing uses.
Sports calendars
Football and American football
A Premier League match kicking off at 12:30 on a Saturday appears on American television at 07:30 EST. A three o’clock kick-off is 10:00 EST. An NFL game played in London at 14:30 local time begins at 09:30 in New York. American viewers with a favourite British club adjust their weekends, and British fans of American football adjust their Sunday evenings.
Formula One and cricket
A Grand Prix starting at 14:00 GMT in Europe is on screens at 09:00 EST. A Test match beginning at 11:00 GMT starts at 06:00 EST. Subtracting five hours is all it takes, provided the date is in the winter period for both countries.
Travel and jet lag
Flying west
A traveller leaving London at 10:00 for a flight of about eight hours lands at 18:00 GMT, which is 13:00 in New York. The body clock still says evening, so the first afternoon feels a long one. Experts recommend staying awake until the local evening and getting daylight early on the next day, and a quick convert GMT to EST on arrival tells you how late it is back home.
Flying east
The reverse trip, leaving New York at 19:00 EST and arriving about seven hours later, lands at 07:00 GMT, which is 02:00 EST on the traveller’s watch. Overnight flights eastward are short in terms of local time, and the loss of five hours is felt more strongly than the gain on the way out.
Remote teams and stand-ups
The fifteen-minute meeting
Distributed software teams often hold a daily stand-up. For a team split between London and New York, the best slot is at 14:30 GMT, which is 09:30 EST. At that hour the Londoners are into their afternoon but not leaving, and the New Yorkers have had coffee but not started deep work.
Documenting it
Write the time in both clocks in the meeting title: “Stand-up 14:30 GMT / 09:30 EST”. In the weeks when the US has moved to EDT and the UK has not, update it to 14:30 GMT / 10:30 EDT. A short convert GMT to EST before each clock change keeps the series honest.
Schools and universities
Online classes across the Atlantic
A lecture starting at 17:00 EST begins at 22:00 GMT. A tutorial at 10:00 EST starts at 15:00 GMT. Exchange students find that coursework deadlines at midnight Eastern are 05:00 GMT the next day, so “submit by midnight” gives British students an extra five hours of sleep.
Exams and deadlines
Examination boards that publish times in Eastern Time and students who take the paper in London need to read the date carefully. An exam at 08:00 EST on 14 January begins at 13:00 GMT on 14 January, a straightforward case, while one at 23:00 EST on 14 January begins at 04:00 GMT on 15 January.
EST, ET and the other American zones
A reference ladder
Central Standard Time is six hours behind GMT, Mountain Standard Time is seven, and Pacific Standard Time is eight. Alaska is nine and Hawaii is ten. When someone says “Eastern”, subtract five. When someone says “Central”, subtract six. When someone says “Pacific”, subtract eight.
Why the abbreviation matters
CST also stands for China Standard Time and Cuba Standard Time, and IST can mean India, Ireland or Israel. Asking “which one?” costs seconds, and guessing wrong costs a missed meeting. For this converter, EST means the Eastern zone of North America.
Radio, television and streaming
Prime time
Prime time on American networks begins at 20:00 EST, which is 01:00 GMT. A show promoted as “tonight at 9” for Eastern audiences reaches London at 02:00 the next morning. Streaming services publish new episodes at fixed instants, and a midnight Eastern release is at 05:00 GMT.
Live events
Awards ceremonies that begin at 20:00 EST are broadcast in Britain in the small hours. To watch an event live from London, set an alarm for 01:00 GMT or choose a recording shown the following day.
Weather and observations
Reading a surface chart
Weather observations are taken at fixed hours in UTC, which weather services often still call GMT. A chart for 12 GMT represents 07:00 EST in New York. A morning snowfall that the New York office reports at 06:00 EST is described in the 11:00 GMT bulletin.
Why the conversion matters
When a forecast says that a front crosses the coast “by 18 GMT”, the local effect in New York comes at 13:00 EST. A traveller who plans a flight for 14:00 EST has about an hour to spare.
Customer service and shipping cut-offs
Order deadlines
Retailers often announce same-day dispatch for orders placed before a cut-off. If the warehouse is in the east of the United States and the cut-off is 14:00 EST, a customer in Britain must order before 19:00 GMT. After that hour, the order joins the next day’s queue.
Support hours
A support desk advertised as open from 08:00 to 20:00 EST is open from 13:00 to 01:00 GMT. A British customer calling at 09:00 GMT will reach a closed line, and one calling at 18:00 GMT will find the desk in full swing.
How to write it unambiguously
Three habits
State the date, the hour and the zone. Use ISO format when you can, such as 2026-01-15 15:00 GMT. Give the other zone in brackets for the reader’s convenience, as in “15:00 GMT (10:00 EST)”.
Avoid shorthand
Phrases like “my morning” or “after lunch” require the reader to know where you are. Replace them with times. If you need to convert GMT to EST for a large mailing list, put a table in the message and let readers find their row.
Checklist: how to convert GMT to EST correctly
Before the calculation
Confirm what GMT means
Is it a technical scale, or the clock in London? If it is the London clock and the date is in summer, treat it as BST and subtract five hours from BST to reach EDT.
Confirm what EST means
Check whether the person means the Eastern zone as a whole or the winter label only. In summer, the Eastern clock is EDT.
After the calculation
Look at the date
If the GMT hour was below five, the answer belongs to the previous day.
Look at the calendar
If the date is in one of the four mismatched weeks, subtract four hours instead of five.
Calendars, invitations and automatic conversion
Let the software do it, then check it
A calendar invitation created in the New York zone and sent to a London address appears at the right hour for the recipient without anybody touching a calculator. The trouble starts when the time is typed into the body of a message. A line such as “Thursday 3 p.m.” has no zone at all, and a reader who guesses their own zone may be five hours out. Write the zone and the date next to the hour, then run the “convert GMT to EST” calculation once as a sanity check.
Files that carry the zone
An invitation file in the iCalendar format stores the instant in UTC or with a named zone, so the reader’s program can display it correctly. A screenshot or a text message does not, and for those the arithmetic on this page is the only safeguard.
Worked examples with a date attached
A Monday in January
A call announced for Monday 12 January at 16:00 GMT takes place at 11:00 EST on the same Monday. Both parties are in winter time, so the five-hour rule holds.
A Sunday in March
A call announced for Sunday 15 March at 16:00 GMT falls in the mismatched weeks, because New York changed its clocks on 8 March. It takes place at 12:00 EDT, so it is four hours behind London, not five.
A Monday in late October
A call announced for Monday 26 October at 16:00 GMT also falls in a mismatched week. London changed back on 25 October, New York changes on 1 November, so the New York clock shows 12:00 EDT.
A Friday in July
A call at 16:00 BST on Friday 17 July is 11:00 EDT. Both sides are on summer time. The gap is again five hours, though the abbreviations differ from the winter ones, and anyone who does a “convert GMT to EST” calculation with the winter labels still reaches the correct number.
Mistakes when you convert GMT to EST
Adding instead of subtracting
New York is behind London, so the New York clock shows an earlier hour. If your result is later than the input, you added five hours by mistake.
Forgetting the date change
Every GMT reading from 00:00 to 04:59 lands on the previous day in New York. A notice for “Friday 02:00 GMT” becomes “Thursday 21:00 EST”.
Applying winter rules in summer
In summer, London and New York both move forward, so the gap remains five hours, but the labels become BST and EDT. A “convert GMT to EST” calculation based on the abbreviations GMT and EST is only correct in winter.
Ignoring the mismatched weeks
In March and late October the gap temporarily falls to four hours. Anyone who relies on a fixed five-hour rule will schedule an hour wrong during those weeks.
Frequently asked questions
What is the difference between GMT and EST?
Five hours. EST is behind GMT.
How do I convert GMT to EST?
Subtract five hours. If the result goes below zero, add twenty-four and use the previous date.
What is 15:00 GMT in EST?
10:00 EST.
Why is the gap sometimes four hours?
Because the United States and Europe switch to summer time on different dates, creating four mismatched weeks a year.
Does my input leave the page?
No. The calculation runs in your browser.
More time zone converters
You may also want Convert GMT to PST, Convert GMT to IST, Convert UTC to EST, Convert EET to EST, Convert EST to UTC, Convert CET to GMT, Convert UTC to WET, Convert GMT to UTC, Convert CET to IST. For the reverse direction, see Convert EST to GMT.
In short, to convert GMT to EST you take off five hours, move to the previous date when the hour is early, and remember that four weeks a year the gap is only four hours. All of it is computed on your own device, free and without an account.