Daylight Saving Time (DST) in the USA
The United States is 1 of about 70 countries around the world using DST. When do clocks change and which areas are exempt? In what year was DST initiated in the US?
March to November
The DST period in the United States begins each year on the 2nd Sunday in March, when clocks are set forward by 1 hour. They are turned back again to standard time on the 1st Sunday in November as DST ends.
Not All Areas Use DST
The Energy Policy Act of 2005 gives every state or territory the right to opt out of using DST.
In the contiguous US, only Arizona currently exercises that right. Clocks in most of the state, including its capital, Phoenix, remain on Mountain Standard Time (MST) all year. The only exception is the Navajo Nation in northern Arizona, which follows DST to stay in sync with the parts of its territory extending into Utah and New Mexico—both states observe DST.
Synchronized but Not Simultaneous
Daylight Saving Time in the United States is synchronized. By law, all areas taking part in the DST switch must do so on the same dates and at the same local time. All clock changes occur at 02:00 (2 am). In the spring, clocks are set forward to 03:00 (3 am); in the fall, they are turned backward to 01:00 (1 am).
However, since the United States spans several time zones, the clock changes, while occurring at the same local time in each time zone, do not happen simultaneously. Eastern time zones switch earlier than western time zones. For example, each DST change happens 3 hours earlier in New York than in Los Angeles.
In Europe, it's the other way around: The continent begins and ends its DST periods at 01:00 Coordinated Universal Time (UTC). This means that each switch occurs at the same moment across Europe—but at different local times.
History: When Did DST Start in the USA?
In 1916, during World War I, Germany became the first country to adopt DST to save energy for the war effort. Many countries across Europe soon followed suit. In the US, “Fast Time”, as it was called then, was first introduced in 1918. The initiative was sparked by Robert Garland, a Pittsburgh industrialist who had encountered the idea in the United Kingdom.
Only 7 months later, DST was repealed. However, some cities, including Pittsburgh, Boston, and New York, continued to use it.
“War Time” and “Peace Time”
In 1942, at the height of World War II, President Franklin D. Roosevelt reintroduced the measure, instituting year-round Daylight Saving Time in the United States. Referred to as “War Time”, DST was in force continuously from February 9, 1942 to September 30, 1945.
During this time, the US time zones were called “Eastern War Time”, “Mountain War Time”, “Central War Time”, and “Pacific War Time”. After the surrender of Japan in mid-August 1945, the time zones were relabeled “Peace Time”.
Uniform Time Act of 1966
From 1945 to 1966, there were no uniform rules for DST in the US. This caused widespread confusion, especially for trains, buses, and the broadcasting industry. As a result, the Uniform Time Act of 1966 was established. While granting US states the ability to opt out of DST, the law provided a framework for a nation-wide, synchronized DST schedule, starting on the last Sunday of April and ending on the last Sunday of October.
DST During the 1973 Oil Embargo
During the 1973 oil embargo, the US Congress ordered a year-round DST period lasting from January 1974 to April 1975. The rationale was to study the effects of seasonal time change on energy consumption. Following staunch opposition from the public and the realization that the measure yielded only modest energy savings, the plan was soon amended to allow for a return to standard time during the winter months.
Energy Policy Act of 2005
After the energy crisis was over in 1976, the DST schedule in the US was revised several times throughout the years. From 1987 to 2006, the country observed DST for about 7 months each year. The current schedule was introduced by the Energy Policy Act of 2005 and has been followed since 2007.