Daylight saving time: everything you need to know

What is daylight saving time?

Daylight Saving Time (DST) is the practice of moving clocks forward by one hour in spring and back by one hour in fall. The purpose is to shift an hour of daylight from the morning to the evening during warmer months, giving people more usable daylight after typical work hours.

In the United States, DST begins in March when clocks "spring forward" at 2:00 AM, and ends in November when clocks "fall back" at 2:00 AM. During DST, the US shifts from standard time abbreviations (EST, CST, MST, PST) to daylight time abbreviations (EDT, CDT, MDT, PDT).

You can check the exact DST dates for any year on our daylight saving time page.

When does daylight saving time start and end?

In 2026, DST starts on Sunday, March 8 at 2:00 AM local time. Clocks move forward from 2:00 AM to 3:00 AM — you lose one hour of sleep.

DST ends on Sunday, November 1 at 2:00 AM local time. Clocks move back from 2:00 AM to 1:00 AM — you gain one hour.

The dates follow a fixed rule established by the Energy Policy Act of 2005: DST begins the second Sunday of March and ends the first Sunday of November. Before 2007, it started in April and ended in October.

Here are the upcoming DST dates:

• 2025: March 9 (spring forward), November 2 (fall back)
• 2026: March 8 (spring forward), November 1 (fall back)
• 2027: March 14 (spring forward), November 7 (fall back)
• 2028: March 12 (spring forward), November 5 (fall back)

Which states don't observe DST?

Two US states do not observe Daylight Saving Time:

Arizona opted out in 1968. The state's reasoning was practical — adding an extra hour of intense desert heat in the evening was undesirable. Arizona stays on Mountain Standard Time (UTC-7) year-round. The exception is the Navajo Nation, which extends into Utah and New Mexico and does observe DST.

Hawaii has never observed DST since the Uniform Time Act of 1966. Being close to the equator, Hawaii's daylight hours don't vary much between seasons, making the time shift unnecessary. Hawaii stays on Hawaii-Aleutian Standard Time (UTC-10) year-round.

Additionally, US territories including Puerto Rico, the US Virgin Islands, Guam, American Samoa, and the Northern Mariana Islands do not observe DST.

The push for permanent DST

Several states have passed legislation to adopt permanent DST, meaning they would stay on "summer time" year-round:

• Florida passed the Sunshine Protection Act in 2018
• Washington passed legislation in 2019
• California voters approved Proposition 7 in 2018

However, all of these require federal approval under the Uniform Time Act. States can opt out of DST entirely (like Arizona), but they cannot adopt permanent DST without Congress changing federal law. The federal Sunshine Protection Act has been introduced multiple times in Congress but has not yet passed.

The debate continues. Supporters argue permanent DST would reduce seasonal depression, cut energy costs, and eliminate the health disruption of biannual clock changes. Opponents note that permanent DST means later sunrises in winter — 8:00 AM or later in many locations — which could be dangerous for children waiting for school buses in the dark.

The history of DST

The concept of adjusting clocks to make better use of daylight is often attributed to Benjamin Franklin, who wrote a satirical essay in 1784 suggesting Parisians could save candle wax by waking earlier. But he never seriously proposed changing clocks.

The modern idea came from New Zealand entomologist George Vernon Hudson in 1895, who wanted extra evening daylight for collecting insects. German Empire adopted DST first in April 1916 during World War I to conserve coal. The UK followed weeks later, and the US adopted it in 1918.

The US has had an inconsistent relationship with DST. It was repealed after both World Wars, reintroduced during the 1973 energy crisis, and standardized nationally only with the Uniform Time Act of 1966. Even then, Indiana didn't fully adopt DST until 2006 — before that, different counties within the state followed different rules.

How DST affects your health

Research consistently shows that the spring clock change disrupts health:

Sleep disruption. Losing one hour in spring takes most adults 5-7 days to fully adjust. The fall change is generally easier because you gain an hour, though even that disrupts sleep patterns.

Heart health. A widely cited study in Open Heart (2014) found a 24% increase in heart attacks on the Monday following the spring time change. The fall change showed a 21% decrease — suggesting the lost hour of sleep is genuinely dangerous.

Accidents. Fatal car accidents increase by about 6% in the week following the spring change, according to a University of Colorado study. Workplace injuries also rise.

Mental health. The November fall-back transition is associated with increased rates of depression, possibly linked to the sudden shift to earlier darkness.

These health impacts are a major argument for eliminating clock changes entirely, whether by adopting permanent standard time or permanent DST.

DST and time zones

DST affects time zone conversions in confusing ways. Not all countries change their clocks on the same dates — or at all.

During the brief windows when the US has changed but Europe hasn't (or vice versa), the time difference between New York and London temporarily shifts. It's normally 5 hours, but for a few weeks in March and October/November, it can be 4 or 6 hours.

Countries in the Southern Hemisphere that observe DST (like Australia) change their clocks in the opposite direction — their DST runs from October to April. This means Sydney is 16 hours ahead of New York during the Northern Hemisphere's winter but only 14 hours ahead during summer.

Always check the world clock for current, accurate time differences that account for DST transitions.

Tips for handling the time change

Before spring forward:
- Shift your bedtime 15 minutes earlier each night for the four nights leading up to the change
- Get extra morning light exposure to help reset your circadian clock
- Avoid alcohol and caffeine in the evening

Before fall back:
- Maintain your regular bedtime even though you "gain" an hour
- Use the extra morning daylight — it helps regulate your internal clock
- Update smoke detector batteries (the traditional reminder)

For parents:
- Shift children's schedules gradually — 10-15 minutes per day over the week before
- Use blackout curtains if morning light disrupts sleep after the change
- Adjust meal times along with bedtimes

For pet owners:
- Pets don't understand clock changes. Shift feeding and walk times by 10-15 minutes per day rather than abruptly.

Frequently asked questions

When do clocks change in 2026?
Spring forward on March 8, 2026. Fall back on November 1, 2026. Both at 2:00 AM local time.

Does DST save energy?
The evidence is mixed. A 2008 US Department of Energy study found DST saves about 0.5% of total electricity — a small but measurable amount. However, some studies show increased air conditioning use offsets lighting savings, particularly in southern states.

Why is it "daylight saving time" and not "daylight savings time"?
The correct term is "daylight saving time" (no 's'). "Saving" is used as a present participle (adjective), like "saving account" or "saving grace." However, "daylight savings time" is so widely used in everyday speech that both forms are commonly understood.

Do other countries observe DST?
About 70 countries observe some form of DST, though the dates vary. The European Union changes clocks on the last Sunday of March and October. Most of Africa, Asia, and South America do not observe DST.

What time zone is Arizona in?
Arizona is in the Mountain Time zone but stays on Mountain Standard Time (MST, UTC-7) year-round. During summer, when neighboring states are on MDT (UTC-6), Arizona is effectively on the same time as Pacific Daylight Time.