Daylight Saving Time in the United States

Last reviewed on May 11, 2026

Daylight saving time (DST) is the practice of shifting clocks forward by one hour during the warmer part of the year so that evening daylight extends later. In the United States, DST runs from the second Sunday in March to the first Sunday in November. During those months, clocks read one hour ahead of standard time — "Eastern Daylight Time" instead of "Eastern Standard Time", and so on for every observing zone.

That's the short version. The longer version is messier: two states and most US territories ignore DST entirely, a few sovereign tribal nations inside non-observing states do follow it, and changing the rules has been a recurring subject of federal and state legislation. This page covers the rules in effect, the well-known exceptions, and what happens at the clock change.

The current rule

The current federal rule comes from the Energy Policy Act of 2005, which extended DST by about four weeks starting in 2007. Under that rule:

• DST begins at 2:00 a.m. local time on the second Sunday in March. Clocks "spring forward" from 1:59 a.m. directly to 3:00 a.m.
• DST ends at 2:00 a.m. local time on the first Sunday in November. Clocks "fall back" from 1:59 a.m. directly to 1:00 a.m., so the hour from 1:00 to 2:00 a.m. happens twice.

Two consequences of how the transitions are written into law are worth knowing. First, the change always happens at 2:00 a.m. local time in each zone, so the country does not switch all at once — Eastern flips an hour before Central, Central flips an hour before Mountain, and so on. Second, the spring change skips an hour of clock time entirely; the fall change adds an hour back. The amount of daylight on those days is essentially unchanged. Only the labels move.

Which states and territories don't observe DST

Federal law allows a state to opt out of DST and stay on standard time year-round, but it does not allow a state to stay on daylight saving time year-round without an act of Congress. As of the date at the top of this page, the following US jurisdictions do not observe DST:

• Arizona — opted out in 1968. The state has cited the extra heat of late-evening summer sunlight as the primary reason.
• Hawaii — never adopted DST. At Hawaii's latitude, day length varies only modestly between summer and winter, so the benefit is small.
• Puerto Rico, US Virgin Islands, Guam, Northern Mariana Islands, and American Samoa — none observe DST. Most lie close enough to the equator that day length is nearly constant year-round.

The territories' time-zone behaviour, including how the dateline affects American Samoa relative to the rest of the US, is covered in more detail on the territories page.

The Arizona exception within the exception

The Navajo Nation, which extends across parts of Arizona, New Mexico, and Utah, observes DST throughout its territory — including the portion inside Arizona, which otherwise does not observe DST. The Hopi Reservation, which is surrounded by the Navajo Nation but is its own jurisdiction, follows Arizona's rule and does not observe DST.

For a small driver in northeastern Arizona, this means it is genuinely possible to change clocks several times in a short distance during the DST months. Most navigation apps handle this automatically; printed timetables can be unreliable.

What "spring forward" actually does to your day

The most common practical questions about the DST transitions:

The spring change (second Sunday of March)

• You "lose" one hour of clock time. A 6-hour overnight period becomes 5 hours on the clock.
• Anything scheduled to happen at 2:30 a.m. local time on that Sunday does not happen, because that wall-clock time does not exist. Cron jobs and automated systems usually handle this by shifting to the next valid time.
• Sunrise and sunset shift one hour later on the clock the morning of the change.

The fall change (first Sunday of November)

• You "gain" one hour of clock time. The hour from 1:00 to 2:00 a.m. local time happens twice.
• Anything scheduled at 1:30 a.m. local time on that Sunday is ambiguous unless the timestamp specifies "before fall back" or "after fall back". Calendar software typically picks the first occurrence.
• Sunrise and sunset shift one hour earlier on the clock that morning.

The Sunshine Protection Act and other legislative efforts

Several states have passed laws that would put them on permanent daylight saving time, but these laws cannot take effect without changes to federal law, because the federal Uniform Time Act of 1966 only permits permanent standard time, not permanent DST, at the state level.

The Sunshine Protection Act is the name of a federal proposal to make daylight saving time permanent nationwide. Versions of it have been introduced repeatedly. The bill has at times passed one chamber of Congress without becoming law. Until a federal bill is signed, the twice-yearly clock change in observing states continues as described above.

State legislation around DST tends to fall into three patterns:

• Opt out entirely — switch to permanent standard time, which states can do unilaterally (Arizona and Hawaii are the standing examples).
• Adopt permanent DST conditional on federal change — many states have laws written this way; they take effect only if federal law changes.
• Stay with the current system — the default position for most states.

Common mistakes

• Assuming "March" means the first Sunday. It is the second Sunday in March and the first Sunday in November — easy to flip.
• Assuming the whole country switches at the same moment. Each zone switches at 2:00 a.m. local time, so Eastern flips three hours before Pacific.
• Forgetting Arizona and Hawaii in summer. During DST, Arizona effectively aligns with Pacific time, and Hawaii is three hours behind Pacific (instead of two).
• Treating "ET" and "EST" as interchangeable in summer. They aren't. See the abbreviations page for the full breakdown.

Why the dates were chosen

The current March-to-November window dates to the Energy Policy Act of 2005 and took effect in 2007, replacing the earlier April-to-October window set by the Uniform Time Act of 1966. The stated rationale at the time was energy savings, although later studies have produced mixed results. The broader history of how the US arrived at the current system is covered on the history page.

Quick reference

• Spring forward: second Sunday of March, 2:00 a.m. local → 3:00 a.m. local.
• Fall back: first Sunday of November, 2:00 a.m. local → 1:00 a.m. local.
• States that don't observe: Arizona (except Navajo Nation), Hawaii.
• Territories that don't observe: Puerto Rico, US Virgin Islands, Guam, Northern Mariana Islands, American Samoa.
• Use the converter to check how a specific time will land in any other US zone.