EST vs EDT: What's the Difference?

EST and EDT are one hour apart

EST is five hours behind Coordinated Universal Time (UTC); EDT is four hours behind. At the same instant, an EDT clock reads one hour later than an EST clock. To convert a time explicitly given in EST to EDT, add one hour. To go from EDT to EST, subtract one hour.

This table compares fixed offsets. New York uses only one of them at a time: 9:00 AM local time means 9:00 AM EST or 9:00 AM EDT, depending on the date. For a dated conversion, use the time zone converter. The UTC to Eastern Time and GMT to Eastern Time pages also follow New York's seasonal rules.

Which months use EST or EDT?

In New York, EDT runs from the March clock change to the November clock change. EST covers the rest of the year, including January and February. March and November each contain both, so a month name alone cannot tell you which offset applies.

Under the current US rules, EDT starts on the second Sunday in March: at 2:00 AM EST, clocks jump to 3:00 AM EDT. It ends on the first Sunday in November: at 2:00 AM EDT, clocks return to 1:00 AM EST. Times in the table use the clock just before each change; each period ends when the next begins.

The highlighted period matches New York at the site's daily build. The dates come from the rules for America/New_York, including the winter periods that cross into another year.

Why “3 PM EST” can mean the wrong time

A summer meeting invitation saying “3 PM EST” is ambiguous if the organizer means New York's local time. Strictly, 3:00 PM EST is 4:00 PM EDT, an hour after a New York meeting scheduled for 3:00 PM. Ask which was intended before converting it. For a recurring meeting, set the calendar's zone to New York so the invitation follows its clock changes.

Logs need a date and an offset too. During the November change, the local hour from 1:00 to 1:59 AM happens twice: first in EDT, then in EST. A timestamp with UTC−04:00 or UTC−05:00 distinguishes the two occurrences. A bare local time cannot.

A sports listing that says “8 PM Eastern” usually means the local Eastern clock on the event date. Check the broadcaster's date and location if the listing says EST during daylight time. Assuming that every appearance of EST means a fixed offset can put the event an hour off on your calendar.

ET vs EST vs EDT

ET means Eastern Time without choosing standard or daylight time. Use it for a schedule that follows the Eastern clock throughout the year, such as “Open at 9 AM ET.” For a single event, include its date; “9 AM ET” alone does not specify a UTC instant.

EST and EDT specify the offset in this North American context. Use EST for standard time and EDT for daylight time. New York and Toronto switch between them. Other places, including Panama, keep UTC−5 all year. Sharing an offset in winter does not mean two places share the same annual rules.

In software, use America/New_York

A time zone ID identifies a set of rules for a place. An abbreviation labels a particular clock reading. For events that should follow New York's local time, use the IANA ID America/New_York; the date then determines whether its offset is UTC−5 or UTC−4.

Using EST as a time zone ID gives different behavior: in the current time zone database, it is an alias for America/Panama, which stays at UTC−5 with no daylight saving changes today. It will not switch to EDT for a New York summer appointment. The legacy ID EST5EDT is now an alias for America/New_York and follows its seasonal changes.

These aliases match this site's build environment. Prefer the location ID in new code so someone reading the configuration can see which place's rules you intend. Store an event's instant with its offset or in UTC, and retain the location zone when future local scheduling matters.

EST in Australia means something else

In Australia, EST can mean Australian Eastern Standard Time, more clearly written AEST: UTC+10. It has no connection to North American EST at UTC−5. Sydney and Melbourne change to Australian Eastern Daylight Time (AEDT), UTC+11, during their summer. Brisbane stays on AEST all year.

Australia's seasons fall at the opposite time of year to New York's. For an invitation involving both countries, write the city and date instead of relying on “EST.” In software, choose Australia/Sydney or Australia/Melbourne for those cities so their own daylight saving rules apply.