The Eastern Time Zone (ET) of the Western Hemisphere falls mostly along the east coast of North America and the west coast of South America. Its time offset is UTC-5 during standard time and UTC-4 during daylight saving time. The clock time in this zone is based on the mean solar time of the 75th degree meridian west of the Greenwich Observatory.

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. 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. In some areas, starting 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 November . In Canada, the time changes as it does in the U.S.