Does the state observe daylight saving time?

How daylight saving time works

Daylight saving time is set by federal law. Under the Uniform Time Act, clocks move forward one hour at 2 a.m. on the second Sunday in March and back at 2 a.m. on the first Sunday in November. Every state follows that schedule unless it passes its own law to opt out. NIST, the federal time lab, notes that daylight saving time now covers 238 days, about 65% of the year; in 2026 it runs from March 8 to November 1.

The opt-out only works one way. A state may exempt itself and stay on standard time all year, either statewide or, in a state that spans two time zones, in the part of the state in one zone. A state that observes daylight saving time must use the federal dates. Federal law does not let a state stay on daylight saving time all year, which is why so many states have passed laws that wait on Congress.

Sources: 15 U.S.C. § 260a, Uniform Time Act (Cornell LII) · NIST: Daylight Saving Time (DST)

How the clock rules got here

Time zones came first. U.S. and Canadian railroads adopted four standard zones in 1883 to end the confusion of local “sun times,” the Congressional Research Service notes. Congress wrote time zones into law in the Standard Time Act of 1918, which also created a summer daylight saving period, following Europe’s wartime lead. After World War I, Congress repealed the federal summer time, but it stayed a local option, and some states kept it.

Year-round daylight saving time has been tried twice. “War Time” began in 1942 and ended on the last Sunday in September 1945. During the 1973 oil embargo, Congress ordered a trial of year-round daylight time starting January 6, 1974. It was cut short: an October 1974 amendment returned the country to standard time from October 27, 1974, to February 23, 1975, and summer-only daylight time came back when the trial ended in 1975.

Before 1966, local choices made a patchwork. In 1961 the Interstate Commerce Commission, then in charge of time zones, told Congress that the “inconvenience, confusion, and sometimes danger” of local option was too high a price. The Uniform Time Act of 1966 set national dates and let a state opt out only as a whole. A 1972 amendment let states split between time zones exempt just one part. Congress moved the start to the first Sunday in April in 1986, and the Energy Policy Act of 2005 set today’s March-to-November schedule, which began in 2007.

Sources: Congressional Research Service: Daylight Saving Time, R45208 (updated July 18, 2019) · 15 U.S.C. § 260a, Uniform Time Act, with statutory notes (Cornell LII)

The states that skip it, and one that joined

Hawaii and most of Arizona don’t observe daylight saving time, and neither do the U.S. territories of American Samoa, Guam, the Northern Mariana Islands, Puerto Rico and the U.S. Virgin Islands, the Congressional Research Service reports. Both states have laws that keep them on standard time all year. The CRS dates Hawaii’s exemption to 1967 and Arizona’s to 1968.

Arizona’s exception has its own exception. NIST notes that the Navajo Nation, which reaches into northeastern Arizona, does observe daylight saving time, so in summer, driving onto the reservation from elsewhere in Arizona means setting the clock ahead an hour.

Indiana went the other way. For many years most of Indiana did not observe daylight saving time, apart from 10 counties, according to a NASA explainer written in 2008. Since 2006, the whole state has changed its clocks. Indiana is still split between Eastern and Central time, and both parts observe daylight saving time.

Sources: Congressional Research Service: Daylight Saving Time, R45208 (updated July 18, 2019) · NIST: Daylight Saving Time (DST) · NASA Eclipse Web Site: Daylight Saving Time (2008)

What the studies show

Congress has asked federal agencies several times whether daylight saving time does what its supporters claim. After the 1974 trial, the Department of Transportation reported that any benefits for energy, traffic safety and crime were small and hard to separate from other changes. The National Bureau of Standards, now NIST, reviewed that study and found no significant energy savings or change in traffic deaths. It did find more morning traffic deaths among school-age children from January to April 1974 than a year earlier, but said the increase could not simply be blamed on the time change.

When Congress lengthened daylight saving time in 2005, it told the Department of Energy to measure the effect. The department’s 2008 report found the extra weeks cut electricity use by about 0.03% in 2007, roughly 0.02% of the country’s total energy use, with larger savings in the north than in the south. It found too little evidence to say whether gasoline use or traffic changed.

Health research has focused on the switch itself. Studies reviewed by the CRS link the spring and fall changes to accumulated sleep loss, and suggest heart attacks may rise briefly after the spring change and dip after the fall one, with some groups at higher risk. In 2023 the American Academy of Sleep Medicine called for ending clock changes in favor of permanent standard time, which it says best fits the body’s internal clock. Twenty other groups endorsed that position, including the National Safety Council and the National PTA.

Sources: Congressional Research Service: Daylight Saving Time, R45208 (updated July 18, 2019) · American Academy of Sleep Medicine: Permanent standard time is the optimal choice for health and safety (position statement) · American Academy of Sleep Medicine: New position statement supports permanent standard time (Oct. 31, 2023)

Waiting on Congress

19 states have enacted laws that would put them on daylight saving time all year once federal law allows it. Most of these laws were passed between 2018 and 2021, and Texas added one in 2025. Until Congress acts, every one of these states still changes its clocks twice a year.

The conditions vary. Many laws need only an act of Congress. Others also depend on neighbors: Oregon waits for both California and Washington, Idaho’s law covers only its Pacific-time panhandle and waits for Washington, and Utah and Wyoming each need several other western states to act. Delaware’s version works differently, moving the state to the Atlantic time zone if New York, Pennsylvania, New Jersey and Maryland do the same, which would keep its clocks at Eastern daylight time all year.

Congress has come close before. The Senate passed an earlier Sunshine Protection Act on March 15, 2022, which would have taken effect November 5, 2023, but it never became law. On July 14, 2026, the U.S. House passed the current version, H.R. 139, by a vote of 308 to 117, with majorities of both parties voting yes. It becomes law only if the Senate also passes it and it is signed.

The bill works by moving each time zone’s standard time one hour later and repealing the seasonal change, so most of the country would keep summer clock time all year. States that now skip daylight saving time, such as Arizona and Hawaii, could choose to keep their current time instead.

Sources: U.S. House Clerk: Roll Call 238 (2026), H.R. 139 Sunshine Protection Act · H.R. 139 (119th Congress), engrossed in House (GovInfo) · S. 623 (117th Congress), Sunshine Protection Act of 2021, engrossed in Senate (GovInfo)

Other routes: Atlantic time and permanent standard time

Because federal law lets a state drop daylight saving time but not keep it, some states have looked at a workaround: move one time zone east, to Atlantic time, and then stop changing clocks. The result would match Eastern daylight time all year. A Massachusetts state commission concluded in 2017 that the state could, under certain circumstances, make a data-driven case for the move. Delaware’s trigger law takes this route, and bills to do the same have been filed in Connecticut and Pennsylvania.

A state can’t move itself into a new time zone, though. Under federal law, the Department of Transportation decides, acting on a request from a state’s governor or legislature, or from county commissioners for a county. The department weighs the “convenience of commerce,” such as where residents work, go to school and get health care, usually holds a hearing in the area, and typically makes any change at a clock changeover. Mercer County, North Dakota, changed zones this way in November 2010.

Other proposals point toward permanent standard time, which federal law already allows. California’s SB 1197 was held in committee in May 2026. Virginia’s SB 541, which would adopt year-round standard time if Maryland and the District of Columbia did the same, passed the state Senate and was then continued to 2027 in a House committee. None of these standard-time bills became law in 2026, so Arizona and Hawaii remain the only states on standard time all year.

Sources: Congressional Research Service: Daylight Saving Time, R45208 (updated July 18, 2019) · California SB 1197 (2025-2026) · Virginia SB 541 (2026)