Eastern Daylight Time (EDT) is a time zone that is four hours behind Coordinated Universal Time (UTC-4). It is observed in the eastern part of the United States and parts of Canada during the summer months when daylight saving time is in effect. EDT typically begins on the second Sunday in March and ends on the first Sunday in November. During this period, clocks are set one hour ahead of Eastern Standard Time (EST), which is UTC-5. The purpose of EDT is to make better use of daylight in the evenings, allowing for longer daylight hours for activities after work or school.