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 central and 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: Eastern Standard Time (EST), which is five hours behind Coordinated Universal Time (UTC−05:00) and observed during late autumn and winter, and Eastern Daylight Time (EDT), which is four hours behind Coordinated Universal Time (UTC−04:00) and observed during spring, summer, and early autumn. Areas in the Eastern Time Zone which do not observe daylight saving time use Eastern Standard Time, which is based on the 75th meridian west of Greenwich. 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.