What this does
Enter a time in GMT (Greenwich Mean Time, the fixed UTC+0 reference) and read it in US Eastern Time. Eastern is 5 hours behind GMT in winter (EST) and 4 hours behind in summer (EDT), because the US side observes daylight saving while GMT never moves.
GMT vs UK local time — an important catch
GMT is a fixed offset and does not change with the seasons. But the UK clock only shows GMT in winter — from late March to late October, Britain is on British Summer Time (BST = UTC+1). So "GMT" can mean two things: the constant UTC+0 reference (used here), or casual shorthand for "the time in London", which is an hour ahead in summer. This page uses the fixed-offset meaning. If you actually want London local time, use the timezone tool and pick Europe/London.
Quick GMT → EST reference
- 12:00 GMT → 7:00 AM EST (winter) / 8:00 AM EDT (summer)
- 15:00 GMT → 10:00 AM EST / 11:00 AM EDT
- 17:00 GMT → 12:00 PM EST / 1:00 PM EDT
- 20:00 GMT → 3:00 PM EST / 4:00 PM EDT
Is GMT the same as UTC?
For everyday clock conversions, yes — both are UTC+0 and read identically. The difference is technical: UTC is an atomic-clock time standard, while GMT is an older astronomical one tied to the Greenwich meridian. No practical gap exists for scheduling. We model GMT here as a fixed, no-daylight-saving zone so the conversion is unambiguous.
Why does the answer change with the date?
Only the Eastern side has daylight saving, so the same GMT time maps to a different Eastern clock depending on whether US DST is active (mid-March to early November). Pick the actual date above and the right offset is applied automatically.
Other directions?
See UTC to EST (numerically identical to this), or the full timezone comparison for more zones.