GMT to EST Converter (and EST to GMT)

About this tool

This page converts GMT to US Eastern Time and Eastern Time to GMT. Because many people say "GMT" when they really mean the time on a UK clock, the converter lets you choose either strict GMT, which is UTC+0 all year, or UK time, which is GMT in winter and British Summer Time (BST) in summer. It starts at 3:00 PM GMT on today's date, shows live clocks, and has a printable chart plus a table of the weeks when London and New York are only 4 hours apart.

How to use the GMT converter

1. Choose what GMT means to you. Pick strict GMT for timestamps and documents that say GMT, or UK time if you are matching a London calendar.
2. Choose the direction and enter the date and time on the side you are converting from.
3. Read the result. The detail line names each zone (Greenwich Mean Time, British Summer Time, Eastern Standard or Daylight Time) with its UTC offset.
4. Use Swap direction to check the reverse without retyping.

GMT, BST and UTC

GMT has an offset of zero, the same as UTC, and never changes. The UK uses it only in winter. According to GOV.UK, UK clocks go forward an hour at 1:00 am on the last Sunday in March, starting British Summer Time, and go back at 2:00 am on the last Sunday in October, returning to GMT. So a London meeting at "3 PM" in July is 3 PM BST, which is 2 PM GMT. If someone writes "GMT" for a summer UK time, they are almost certainly an hour off, and you should confirm which they mean.

Why GMT to EST is 5 hours, and sometimes 4

Strict GMT is easy: Eastern Standard Time is 5 hours behind it, and Eastern Daylight Time 4 hours behind. With UK time it gets more interesting. In winter it is GMT against EST, 5 hours apart. In summer it is BST against EDT, also 5 hours apart, because both sides moved forward by an hour. But the US changes its clocks on the second Sunday in March and the first Sunday in November (NIST), while the UK changes on the last Sundays of March and October. In the weeks between, one country has switched and the other has not, and the gap shrinks to 4 hours.

In 2026 that happens from Sun Mar 8, 2026 to Sun Mar 29, 2026 (20 days) in spring, and from Sun Oct 25, 2026 to Sun Nov 1, 2026 (7 days) in autumn. In 2027 the spring window is shorter, from Sun Mar 14, 2027 to Sun Mar 28, 2027, and the autumn window runs from Sun Oct 31, 2027 to Sun Nov 7, 2027. The exact switch times are in the table below the chart. Recurring transatlantic calls drift by an hour for one side during these weeks, so it is worth checking with the converter set to UK time.

Worked example: 3 PM GMT

The converter opens with strict GMT and 3:00 PM. On a summer date it shows 3:00 PM GMT = 11:00 AM EDT, with the detail that Eastern Time is 4 hours behind GMT, at UTC-04:00. On a winter date it shows 3:00 PM GMT = 10:00 AM EST, 5 hours behind. Now switch "GMT means" to UK time on that summer date: 3:00 PM becomes 3:00 PM BST = 10:00 AM EDT, because London is on summer time too.

Common mistakes

• Using GMT and UK time interchangeably in summer. They differ by an hour from late March to late October.
• Assuming London and New York are always 5 hours apart. Calendar apps handle the 4-hour weeks correctly, but mental math and fixed spreadsheet offsets do not.
• Writing "EST" for a summer New York time. Between March and November it is EDT.
• Forgetting that early-morning GMT times are the previous evening in New York; 2:00 AM GMT is 9:00 PM EST the day before.

Use cases

Planning calls between London and New York offices, converting a match or race start time published in GMT or UK time, and reading documents that quote GMT deadlines. For strict UTC timestamps, see UTC to EST; for more cities at once, use the Time Zone Converter. India-based teams can use EST to IST.