Twice a year, the same argument returns. Europe and the UK set their clocks back on Sunday, October 25, 2026, and the United States and most of Canada follow on Sunday, November 1. Almost everyone agrees that changing the clocks is annoying. Far fewer people agree on what should replace it. Should the clocks stay on summer time all year, with brighter evenings, or on standard time, with brighter mornings?
The answer turns out to be less obvious than either camp suggests. Sleep scientists, economists, and governments have looked closely at this question, and several countries have already tried each option. This comparison sets out what actually changes, what the evidence says about sleep, safety, and energy, and what happened in the places that picked a side.
What Actually Changes When the Clocks Change
Changing the clocks does not create or remove a single minute of daylight. A day in Chicago in December is just as short whatever the clock says. What the change does is move daylight from one end of the day to the other, relative to the hours when people get up, go to school, and go to work.
Standard time puts the clock close to the sun: noon on the clock is roughly when the sun is highest. Daylight saving time shifts everything one hour later, so the sun rises and sets one hour later on the clock. In summer, that turns a 4 a.m. sunrise nobody sees into a 5 a.m. one and adds an hour of evening light. In winter, the same shift pushes sunrise toward 8 or even 9 a.m. in the northern and western parts of many time zones, when children are already on their way to school.
That is the core trade-off of the whole debate. You cannot have both bright winter mornings and bright winter evenings. Every option is a choice about which part of the day gets the light.
Daylight Saving Time vs Standard Time at a Glance
|
Factor |
Standard time |
Daylight saving time |
|---|---|---|
|
Clock vs sun |
Clock noon is close to solar noon |
Clock runs about one hour ahead of the sun |
|
Morning light |
Earlier sunrise, more light before work and school |
Later sunrise, darker mornings |
|
Evening light |
Earlier sunset |
One extra hour of evening light |
|
Body clock |
Aligns better with natural light cycles |
Pushes the body clock later, especially for teenagers |
|
Main appeal |
Health, sleep, safer winter mornings |
After-work leisure, outdoor activity, retail |
|
Main drawback |
Very early summer sunrises, dark late afternoons in winter |
Very late winter sunrises |
What Sleep Scientists Say
The clearest institutional position comes from the American Academy of Sleep Medicine. In a 2020 position statement, it called for ending seasonal clock changes in favor of permanent standard time, not permanent daylight saving time. Many other sleep and medical organizations have since supported that view.
The reasoning comes down to how the body clock works. The internal circadian clock runs slightly longer than 24 hours and is reset every day mainly by light. Morning light pulls the body clock earlier and helps people feel sleepy at a reasonable hour. Evening light pushes it later. Daylight saving time takes light from the morning and adds it to the evening, which is the combination that delays the body clock most. School, work, and alarm clocks, however, don’t move later. The result is a persistent gap between when the body wants to sleep and when people have to get up. Researchers call this “social jet lag.” Teenagers, whose body clocks naturally run later, are hit hardest.
Permanent standard time is not perfect either. In summer it brings very early sunrises: in Boston, the sun would rise just after 4 a.m. in June. For people with blackout curtains, that hardly matters. For light sleepers, it can be a real cost. The scientific case for standard time rests on the morning light it gives in winter, not on summer comfort.
The Week After the Change: Why Spring Is Worse Than Fall
Much of the public frustration with clock changes is really frustration with the transitions themselves, and the two transitions are not equal.
The spring change costs an hour of sleep and forces the body clock to adjust in its harder direction. The best-known evidence of its effect comes from a 2020 study by Josef Fritz, Céline Vetter, and colleagues at the University of Colorado Boulder, published in Current Biology. They analyzed 732,835 fatal car accidents in the United States from 1996 to 2017 and found a 6% higher risk of fatal crashes in the week after the spring change, about 28 extra deaths per year. Most of the extra accidents happened in the morning. When the US moved the spring change from April to March in 2007, the spike moved with it, which makes the time change the most likely cause.
The same study found no comparable effect after the autumn change. Falling back gives an extra hour and moves the body clock in its easier direction. This matters for the debate: if the spring transition is the main problem, ending clock changes in either direction removes it. The choice between permanent standard and permanent daylight time is a separate question about the other 51 weeks of the year.
The Energy Myth
Daylight saving time was introduced during World War I as an energy-saving measure, and that justification is still repeated. Modern evidence doesn’t support it.
The most cited study is a natural experiment in Indiana, where many counties did not observe daylight saving time until 2006. Economists Matthew Kotchen and Laura Grant analyzed more than 7 million monthly household electricity bills before and after the switch and published the results in The Review of Economics and Statistics in 2011. They found that daylight saving time increased household electricity use by about 1% overall, and by 2% to 4% in the fall, costing Indiana households an estimated $9 million per year. The savings on evening lighting were outweighed by extra heating on dark mornings and extra air conditioning on longer, warmer evenings.
Other studies have found small savings rather than small losses. A 2008 US Department of Energy report on the 2007 extension of daylight saving time estimated savings of about 0.03% of annual US electricity use. Taken together, the evidence suggests that the effect on energy is close to zero in either direction. Neither side of the debate should rely on energy savings as its main argument.
Permanent Daylight Saving Time vs Permanent Standard Time
Most current proposals are not about keeping the twice-yearly change. They are about which time to make permanent. Here is how the two options compare:
|
Factor |
Permanent standard time |
Permanent daylight saving time |
|---|---|---|
|
Winter mornings |
Light by the usual school and commute hours in most places |
Dark until around 8 to 9 a.m. in many northern and western cities |
|
Winter evenings |
Sunset around 4 to 5 p.m. in many cities |
One extra hour of light after work |
|
Summer mornings |
Sunrise as early as about 4 a.m. in the far northeast of the US |
Same as today’s summer time |
|
Sleep science |
Favored by the American Academy of Sleep Medicine |
Opposed by most sleep organizations |
|
US legal status |
Already allowed: states can opt in (Arizona, Hawaii) |
Requires an act of Congress |
|
Track record |
Mexico since 2022, Arizona since 1968 |
The US tried it in 1974 and abandoned it within a year |
What Happened in the Places That Chose
The United States, 1974: permanent daylight time lasts ten months
During the oil crisis, Congress put most of the country on year-round daylight saving time beginning January 6, 1974. In December 1973, the National Opinion Research Center at the University of Chicago found 79% of Americans in favor. By February 1974, support had fallen to 42%. Children were walking to school in the dark, and several fatal accidents involving children drew national attention. In October 1974, President Gerald Ford signed legislation returning the country to standard time for the winter. The experiment that was meant to last two years ended after about ten months.
Alberta, 2021: a referendum decided by 5,092 votes
In October 2021, the Canadian province of Alberta held a referendum asking whether it should adopt year-round daylight saving time. According to Elections Alberta, 531,782 voters (49.8%) said yes and 536,874 (50.2%) said no, so Albertans kept changing their clocks. The result shows how evenly divided public opinion is. Critics of the vote argued that many people who wanted to stop changing the clocks still did not want permanent summer time, a distinction that a single yes-or-no question cannot capture.
Mexico and Turkey: two opposite choices
Mexico ended daylight saving time for most of the country in 2022, effectively choosing permanent standard time; only Baja California and some municipalities on the US border still follow the US schedule. Turkey went the other way in 2016, staying permanently on UTC+3, effectively year-round summer time. As a result, winter sunrises in Istanbul come after 8 a.m.
Iceland and Japan: no clock changes at all
Some countries simply do without seasonal changes. Iceland has kept the same time year-round since 1968, and Japan has not used daylight saving time since 1951. Neither is debating whether to bring it back.
Where the Debate Stands in 2026
In the United States, the Sunshine Protection Act, which would make daylight saving time permanent, passed the House of Representatives on July 14, 2026, by 308 votes to 117, with public support from President Trump. The Senate passed an earlier version in 2022, but it never received a House vote. This time the bill is waiting in the Senate. Unless the Senate passes it and the president signs it in time, the November 1 change goes ahead. Note that the bill chooses the option sleep scientists oppose and that the country abandoned in 1974.
In Europe, the European Parliament voted in 2019 to end seasonal clock changes, but EU member states have never agreed whether to stay on summer or winter time. Spain pushed the issue again in October 2025, but no decision has been made, and the October 25 change will happen as usual. The UK, outside the EU, has no current plans to change its system. Because the dates and the rules keep changing, it is worth checking the exact date and local time of each change on WorldTimeData before booking travel or scheduling meetings across borders. WorldTimeData lists current local times and the next clock change for countries around the world.
How to Get Through the Week After the Clock Change
While the debate continues, the clocks will keep changing. A few habits based on the same circadian science make the transitions easier:
-
Get outdoor light early. Morning daylight is the strongest signal for resetting the body clock. A 15 to 30 minute walk soon after waking helps more than any app.
-
Shift gradually before the spring change. Moving bedtime and wake-up time 15 to 20 minutes earlier each day for three or four days spreads the lost hour out instead of absorbing it in one night.
-
Keep your wake-up time steady in the fall. The extra hour feels like a gift, but sleeping in on Sunday and Monday makes the adjustment slower. Getting up at the usual clock time lets the body clock catch up within a few days.
-
Be careful on the road in the spring. The crash data points to the mornings of the first workweek after the spring change. Allow extra time and avoid driving drowsy.
-
Dim the evening lights. Bright screens and lighting late in the evening push the body clock later, which works against adjusting after either change.
-
Watch children and teenagers. Their body clocks run later and their sleep schedules are often already tight. An earlier bedtime for a few nights before the spring change helps more than catching up on sleep afterward.
