Eastern Time Zone

The Eastern Time Zone (ET) is a time zone encompassing part or all of 23 states in the eastern United States, parts of eastern Canada, some Caribbean islands and the state of Quintana Roo in Mexico. Most areas in the time zone observe daylight saving time and thus alternate between:

Areas in the Eastern Time Zone which do not observe daylight saving time use Eastern Standard Time. Observation of daylight saving time starts on the second Sunday in March, at 2:00 a.m. EST, clocks are advanced to 3:00 a.m. EDT, creating a 23-hour day. On the first Sunday in November, at 2:00 a.m. EDT, clocks are moved back to 1:00 a.m. EST, which results in a 25-hour day.

The time in this zone is based on the mean solar time of the 75th meridian west of the Royal Observatory, Greenwich.

The boundaries of the Eastern Time Zone have moved westward since the Interstate Commerce Commission (ICC) took over time-zone management from railroads in 1938. The easternmost and northernmost counties in Kentucky were added to the zone in the 1940s, and in 1961 most of the state went Eastern. In 2000, Wayne County, on the Tennessee border, switched from Central to Eastern Time. Within the United States, the Eastern Time Zone is the most populous region, with nearly half of the country's population.

In March 2019, the Florida Legislature passed a bill requesting authorization from Congress for year-round daylight saving time, which would effectively put Florida on Eastern Daylight Time year-round (except for west of the Apalachicola River, which would be on Central Daylight Time year-round). A similar bill was proposed for the Canadian province of Ontario by its legislative assembly in late 2020, which passed though was placed on hold until Quebec and New York agreed to make the same change, which had not happened as of 2024.

For those in the United States, daylight saving time for the Eastern Time Zone was introduced by the Uniform Time Act of 1966, which specified that daylight saving time would run from the last Sunday of April until the last Sunday in October. The act was amended to make the first Sunday in April the beginning of daylight saving time beginning in 1987. Later, the Energy Policy Act of 2005 extended daylight saving time in the United States, beginning in 2007.

In Canada, the following provinces and territories are part of the Eastern Time Zone:

Within Canada, as with the United States, the Eastern Time Zone is the most populous time zone. Most of Canada observes daylight saving time synchronously with the United States, with the exception of Saskatchewan, Yukon, and several other very localized areas. Southampton Island in Nunavut uses Eastern Standard Time throughout the year.