Daylight saving time in the United States

Daylight saving time in the United States
Harris & Ewing Collection · Public domain · source
Name	Daylight saving time in the United States
Observed by	United States
Begins	Second Sunday in March
Ends	First Sunday in November
First implemented	1918
Legislation	Standard Time Act of 1918, Uniform Time Act of 1966, Energy Policy Act of 2005

Daylight saving time in the United States is the practice of advancing clocks during part of the year to extend evening daylight, observed in most of the United States with exceptions. Its adoption has been shaped by wartime measures, federal statutes, state legislation, and debates involving energy policy, public health, and commerce.

History

Initial experiments with seasonal time adjustment in the United States occurred in the early 20th century amid discussions in Congress and advocacy by figures such as Benjamin Franklin (in earlier satire), George Hudson (international influence), and proponents associated with the National Daylight Saving Association. The first nationwide statutory implementation came with the Standard Time Act of 1918 during World War I under President Woodrow Wilson, driven by coordination with the United Kingdom, France, and Germany for wartime efficiency. Opposition from rural interests and state legislatures led to repeal of the federal mandate after the war, producing a patchwork of local observance similar to the disputes seen in the Gilded Age over infrastructure.

During World War II, President Franklin D. Roosevelt instituted year-round daylight saving called "War Time" to aid war production and align with practices in Soviet Union and United Kingdom. Postwar inconsistency persisted until the Uniform Time Act of 1966, signed by President Lyndon B. Johnson, which standardized start and end dates while allowing state opt-outs, echoing earlier debates in the Progressive Era about federal versus state authority. States continued to experiment: Indiana's complex county-level alignments became notable in the late 20th century, involving legal disputes with the Department of Transportation.

The Energy Policy Act of 2005, enacted during President George W. Bush's administration, extended daylight saving by shifting the start to the second Sunday in March and the end to the first Sunday in November, a change debated in hearings involving the Department of Energy, National Highway Traffic Safety Administration, and elected officials such as members of the United States Senate and United States House of Representatives.

Implementation and observance

Observance varies by jurisdiction: most of the contiguous United States follows federal rules, while notable exceptions include Hawaii and most of Arizona (except the Navajo Nation). Territories such as Puerto Rico, Guam, American Samoa, and the United States Virgin Islands do not observe daylight saving. State legislatures in Florida, California, Texas, New York, and Massachusetts have considered or passed measures requesting year-round daylight time, subject to Congressional approval because of federal authority under the Commerce Clause and the Standard Time Act of 1918 amendments.

Local governments, utilities, airlines including American Airlines, rail carriers such as Amtrak, broadcasters regulated by the Federal Communications Commission, and financial markets like the New York Stock Exchange coordinate transitions to avoid disruption. Software and standards bodies including Internet Engineering Task Force and vendors such as Microsoft, Apple Inc., Google and IANA maintain time zone databases to reflect changes; international entities such as International Air Transport Association track adjustments for scheduling.

Legal framework and legislation

Federal authority over time zones and daylight saving derives from statutes: the Standard Time Act of 1918 established time zone boundaries, the Uniform Time Act of 1966 standardized observance, and the Energy Policy Act of 2005 altered dates. The Department of Transportation administers time zone boundaries and exemptions; litigation over state actions has reached federal courts and involved plaintiffs including state governments and private parties.

State legislatures in Arizona, Hawaii, Florida, Alaska, California, Illinois, Ohio, Michigan, Pennsylvania, and Virginia have passed resolutions or statutes seeking permanent daylight time, often citing testimony filed with committees of the United States Senate and United States House of Representatives. International agreements, airline accords, and interstate commerce considerations implicate entities such as the Department of Commerce and the Federal Aviation Administration when assessing impacts.

Effects and controversies

Economic, health, and safety effects are debated across research published by institutions such as the National Institutes of Health, the Centers for Disease Control and Prevention, the National Bureau of Economic Research, and universities including Harvard University, Stanford University, University of California, Berkeley, Johns Hopkins University, and Columbia University. Studies link transitions to short-term increases in traffic accidents examined by the National Highway Traffic Safety Administration, shifts in energy consumption assessed by the Department of Energy, and impacts on sleep, circadian rhythms, and cardiovascular events analyzed by researchers collaborating with the American Heart Association and the Sleep Research Society.

Controversies involve partisan and industry stakeholders including labor unions, agricultural interest groups like the American Farm Bureau Federation, retail associations such as the National Retail Federation, and public safety organizations including local police departments. Legislative crusades by senators and representatives from states such as Florida and Arizona have prompted hearings in committees of the United States Senate Committee on Commerce, Science, and Transportation and the House Committee on Energy and Commerce. Advocacy organizations and think tanks such as the Brookings Institution and the Heritage Foundation have published policy analyses arguing for or against permanent changes.

Time zones and boundaries

Time zone boundaries across the United States—including Eastern Time Zone, Central Time Zone, Mountain Time Zone, Pacific Time Zone, Alaska Time Zone, and Hawaii–Aleutian Time Zone—are set by federal regulation administered by the Department of Transportation. Border regions such as counties in Idaho, Oregon, Michigan, Indiana, and Kentucky have experienced disputes and petitions involving state governors, county commissions, and the DOT. International border synchronization with Canada (provinces like Ontario and Quebec), Mexico (states like Chihuahua and Sonora), and territories informs cross-border commerce and transportation managed by agencies including U.S. Customs and Border Protection and Transport Canada.

Category:Time in the United States