Daylight Saving Time in the US
The US is one of about 70 countries around the world using Daylight Saving Time (DST), but Hawaii and most of Arizona don't use it.
Arizona is the only state in mainland US that does not use DST. But there are exceptions.
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When Does DST Start and End?
DST in the United States begins each year on the second Sunday in March when clocks are set forward by 1 hour. They are turned back again to standard time on the first Sunday in November as DST ends.
Not All States Use DST
Almost all of the United States has yearly clock changes. The only exceptions are Hawaii, where Hawaii Standard Time (HST) is observed all year, and most of Arizona, which follows Mountain Standard Time (MST) year-round. In Arizona, only the Navajo Nation uses DST to stay in sync with its territory extending into Utah and New Mexico—both states that observe DST.
Indiana, after having abstained from changing its clocks since 1970, decided to join the national DST regime in 2006.
None of the US dependencies use DST, including American Samoa, Guam, Puerto Rico, the Northern Marina Islands, the US Minor Outlying Islands, and the US Virgin Islands.
Some States Want to Remove DST
Proposals to stay on standard time or move to full-time DST appear on the US legislative agenda nearly every clock change. Since 2015, more than 200 bills and resolutions related to Daylight Saving Time have been introduced, covering almost every state across the US, according to the National Conference of State Legislatures.
Recently, several states have proposing or passed bills in favor of permanent DST. However, they need congressional approval to abolish the time change. For this to happen, Congress first has to pass a federal law allowing states to observe DST year-round, because today's law, the Energy Policy Act of 2005, only allows states to opt out of DST.
Does DST Start at the Same Time?
By law, all clock changes in the US occur at 02:00 (2 am), in the state's local time. In spring, clocks are set forward to 03:00 (3 am); they are turned backward to 01:00 (1 am) in the fall.
However, since the US 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 UTC. This means that the DST change happens simultaneously 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. But 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 US. 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.”
National DST Rules since 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.
Year-Round DST in 1973
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 United States DST schedule 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.