EST vs EDT: What’s the Difference?
EST and EDT both refer to US Eastern Time — the same place, the same time zone database entry, just a different offset depending on the time of year.
EST (Eastern Standard Time) and EDT (Eastern Daylight Time) both describe the same US East Coast time zone — cities like New York, Boston, and Miami. They are not two separate zones; they’re the same zone at two different points in the year.
The offsets
- EST (standard time, roughly November–March): UTC−5
- EDT (daylight saving time, roughly March–November): UTC−4
The underlying identifier — America/New_York in the IANA time zone database — never changes. Only the offset shifts with the calendar, exactly when daylight saving time starts and ends.
This is why "EST" and "EDT" are unreliable as identifiers on their own: if someone gives you a meeting time in "EST" during summer, they likely mean the local Eastern Time regardless of which abbreviation is technically correct. Timemazone always resolves to America/New_York and shows you the correct current offset, rather than trusting the label.