In the United States and Canada, this time zone is generally called Eastern Time (ET). Specifically, it is Eastern Standard Time (EST) when observing standard time (Winter), and Eastern Daylight Time (EDT) when observing daylight saving time (Summer). The 1966 Uniform Time Act in the USA meant that EDT was instituted on the last Sunday in April, starting in 1966, throughout most of the USA.1 EST would be re-instituted on the last Sunday in October. The act was amended to make the first Sunday in April the beginning of EDT as of 1987.1 The Energy Policy Act of 2005 extended daylight saving time in the U.S. beginning in 2007. The local time changes at 02:00 EST to 03:00 EDT on the second Sunday in March and returns at 02:00 EDT to 01:00 EST on the first Sunday in November1. In Canada, the time changes as it does in the U.S.2
In the United States, the following states (or federal district, in the case of the District of Columbia) are part of the Eastern Time Zone in their entirety:
The exact specification for the location of time zones and the dividing line between zones is set forth in the Code of Federal Regulations at 49 CFR 71.3
North American Eastern Time Zone (shown in the furthest right yellow)
Parts of several other states use Eastern Time as well:
nearly all of Florida except for the part of the panhandle west of the Apalachicola River. Approaching the Gulf of Mexico, the line jumps west to the Bay/Gulf county line.
Eastern Time is also used somewhat as a de-facto official time for all of the United States. National 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. 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. Most cable channels advertise their times for their shows in Eastern time, leaving residents in the other time zones to figure out what time it is in their time zone for themselves.
^ The specification for the Eastern Time Zone is set forth at 49 CFR 71.4, and is listed in Text and pdf formats.
The boundary between Eastern and Central is set forth at 49 CFR 71.5, and is listed in text and pdf formats.