The Eastern Time Zone (ET) is a time zone encompassing 17 U.S. states in the eastern part of the contiguous United States, parts of eastern Canada, the state of Quintana Roo in Mexico, Panama in Central America, and the Caribbean Islands.
In the northern parts of the time zone, on the second Sunday in March, at 2:00 a.m. EST, clocks are advanced to 3:00 a.m. EDT leaving a one-hour "gap". On the first Sunday in November, at 2:00 a.m. EDT, clocks are moved back to 1:00 a.m. EST, thus "duplicating" one hour. Southern parts of the zone (Panama and the Caribbean) do not observe daylight saving time.
The boundaries of the Eastern Time Zone have moved westward since the Interstate Commerce Commission took over time-zone management from railroads in 1938. For example, 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. In March 2018, the Florida Legislature passed a bill requesting authorization from Congress for year-round daylight savings time, which would effectively put Florida on Atlantic Standard Time year-round.
The Uniform Time Act of 1966 ruled that daylight saving time would run from the last Sunday of April until the last Sunday in October in the United States. The act was amended to make the first Sunday in April the beginning of daylight saving time as of 1987. The Energy Policy Act of 2005 extended daylight saving time in the United States beginning in 2007. So local times change at 2:00 a.m. EST to 3:00 a.m. EDT on the second Sunday in March and return at 2:00 a.m. EDT to 1:00 a.m. EST on the first Sunday in November. In Canada, the time changes as it does in the United States.
All observe Daylight Saving Time in sync with the United States, with very localized exceptions.
Seventeen states and Washington, D.C. are located entirely within the Eastern Time Zone, they are:
Five states are partly in both the Eastern Time Zone and the Central Time Zone, they are:
 Eastern Time is also used somewhat as a de facto official time for all of the United States because it includes the capital city (Washington D.C.), the most populous city (New York City), and half of the country’s population. For this reason, media organizations will often report when events happened or are scheduled to happen in Eastern Time even if they occurred in another time zone, and TV schedules are also almost always posted in Eastern Time. In the United States, all nationally televised morning programs (except Good Morning America Weekend Edition which some ABC affiliates on the east coast air on a tape-delay), some daytime talk shows, evening newscasts, most talent and awards shows, and any other nationally televised event that airs live on American television during prime time and on the weekends (such as sports television) are broadcast live in the Eastern Time Zone. Major professional sports leagues also post all game times in Eastern time, even if both teams are from the same time zone, outside of Eastern Time. For example, a game time between two teams from Pacific Time Zone will still be posted in Eastern time (for example, one may see "Seattle at Los Angeles" with "10:00 p.m." posted as the start time for the game, often without even clarifying the time is posted in Eastern time).
Most cable television and national broadcast networks advertise airing times in Eastern time. National broadcast networks (ABC, CBS, The CW, FOX, NBC) generally have two primary feeds, an eastern feed for Eastern and Central time zones, and a tape-delayed western feed for the Pacific Time Zone. The prime time is set on Eastern and Pacific at 8:00 p.m., with the Central time zone stations receiving the eastern feed at 7:00 p.m. local time. Mountain Time Zone stations receive a separate feed at 7:00 p.m. local time. As Arizona does not observe daylight saving time, during the summer months, it has its own feed at 7:00 p.m. local time. Cable channels with a separate western feed (such as HBO, whose western feed is called "HBOW") generally air the same programming as the eastern feed delayed by three hours. Other cable networks such as the Discovery family of networks repeat their prime time programming three hours later; this allows for the same show to be advertised as airing at "8:00 p.m. E/P" (that is, "8:00 p.m. Eastern and Pacific time"). Networks specializing in the airing of sports events, such as ESPN, advertise all of their programming in Eastern and Pacific, incorporating the 3-hour time difference (as in "8:00 p.m. Eastern/5:00 p.m. Pacific") and leaving viewers in the remaining time zones to calculate start time in their own areas.
The Bahamas officially observe both Eastern Standard Time during the winter months and Eastern Daylight Time during the summer months. Cuba is usually the same, with Eastern Standard Time in the winter, and Eastern Daylight Time in the summer, but it often changes on different days. Cayman Islands, Haiti, and Jamaica use Eastern Standard Time year-round. The Turks and Caicos Islands used to follow eastern time with daylight saving but switched in 2015 to the Atlantic Time Zone.
Panama in Central America uses Eastern Standard Time UTC−05 year-round. The state of Acre and the southwest part of the state of Amazonas all in Brazil as well as Colombia, Ecuador (except for the Galápagos Islands, which uses Central Standard Time), and Peru in South America also use EST (UTC−5) all year-round.
Time zones in North America
|Time zone||Hours from UTC: Standard time||Hours from UTC: Daylight saving time|
|Hawaii–Aleutian (in Hawaii)||–10||–10|
|Hawaii–Aleutian (in Alaska)||–10||–9|
|Mountain (Arizona and Sonora only)||–7||–7|
|Mountain (other states/provinces)||–7||–6|
|Central (Saskatchewan only)||–6||–6|
|Central (other states/provinces)||–6||–5|
|Eastern (parts of Nunavut and the Caribbean)||–5||–5|
|Eastern (other states/provinces)||–5||–4|
|Atlantic (Natashquan River)||–4||–4|
|Atlantic (other states/provinces)||–4||–3|
|Saint Pierre and Miquelon
and most of Greenland