It’s Almost Time to Change Your Clock Again

Why daylight saving time endures — and a permanent switch has yet to take hold.

“Spring forward, fall back” is a twice-a-year part of life in roughly 70 countries around the world. In the US, where the practice is more than a century old, lawmakers are considering measures that would end clock changes and make daylight saving time permanent. That would mean later sunrises and sunsets for half the year. There’s evidence that the public health effect would be mixed: fewer car accidents and heart attacks caused by time shifts, but potentially a loss of sleep quality for almost everyone in winter. The history of the issue both in the US and around the world shows that no approach is likely to make everybody happy.

What’s the purpose of daylight saving time?

Daylight saving time changes how our timepieces align with the longer hours of sunshine that come in summer. It allows people to enjoy more light in the evening, rather than sleeping through it in the early morning, without changing their schedules. US inventor and diplomat Benjamin Franklin is often credited with inspiring the concept. He wrote an essay in 1784 suggesting a change in sleep routines to reduce candle consumption in the evening. Daylight saving time was first adopted as official policy by Germany during World War I, with the aim of conserving energy.

When does it start in 2025?

In the US in 2025, daylight saving time starts at 2 a.m. on Sunday, March 9. Standard time resumes on Sunday, Nov. 2. Europe switches to daylight saving on March 30.

What are the origins of daylight saving time in the US?

The US adopted the time change in 1918, with Congress initially letting the states decide when their periods of extra evening light would begin and end. (Contrary to popular belief, farmers didn’t support the measure, as clock changes disrupted their work schedules.) In 1966, Congress passed the Uniform Time Act, which standardized the start and end of daylight saving time across the country — or most of it, since any state could exempt itself. Hawaii opted out and chose to stay on standard time year-round, as did Arizona, except for the lands of the Navajo Nation. In 2005 the daylight saving period was expanded to the current schedule, running from the second weekend in March through the first weekend in November.

What changes are lawmakers in the US considering?

In January, US Senator Rick Scott, a Florida Republican, introduced a new version of the Sunshine Protection Act, which would make daylight saving the new, standard time and end the practice of changing clocks. In 2022, the Senate passed a previous version of the bill, but it stalled in the House of Representatives.

Beginning with Florida in 2018, 20 states have passed laws or resolutions that would put them on permanent daylight saving time if federal law allows it and, in some cases, if surrounding states took the same action. Some states have debated moving in the other direction by eliminating clock changes and dropping daylight saving time.

Eliminating twice-yearly clock changes at times has had the support of another key constituent, President Donald Trump, who posted “Making Daylight Saving Time permanent is O.K. with me!” on social media in 2019. A follow-up post in December 2024 — “The Republican Party will use its best efforts to eliminate Daylight Saving Time” — was generally interpreted as a call to end clock changes.

What would be the benefits of permanent daylight saving time in the US?

Permanent daylight saving time would spare everyone from having to remember to change their clocks and from missing appointments if they forgot to do so. It would also provide an extra hour of sunlight in the winter for outdoor activities after school and work. Proponents say there would be public health and economic benefits. Studies have shown that the “spring forward,” in particular, disrupts the body’s internal clock, disturbing sleep cycles and increasing the risks of car crashes caused by fatigue, as well as heart attacks and strokes. A study analyzing 20 years of US government data found that there were about 6% more fatal crashes in the week after the spring-ahead change. Some economists say restaurants, retail shops and leisure businesses such as golf clubs would benefit from the extra daylight during winter evenings. According to a report by the JPMorgan Chase Institute, shoppers spend 3.5% less in retail stores in the month following the fall shift back to standard time.

What are the arguments against permanent daylight saving time?

The extra evening sunlight in the winter would come at a cost: darker mornings. That would mean more moonlit commutes — especially in the northwest corner of each time zone in the contiguous US, where the sun would rise as late as around 10 a.m. The American Academy of Sleep Medicine has come out against permanent daylight saving time, arguing that the human body’s internal clock is more suited to standard time. It called for eliminating daylight saving time and thus clock changes.

How does the rest of the world handle this?

All countries in the European Union, much of North America and some in South America change their clocks. Much of Asia, including China, India and Japan, experimented with daylight saving time during the 20th century, only to abandon the practice. Most of Africa has never used it. In 2019, the European Parliament strongly backed a proposal to end the clock changes, but the measure got sidelined by other priorities, including the Covid-19 pandemic. Countries near the equator generally forgo daylight saving because sunrises and sunsets there vary little from season to season.

Mexico stopped switching to daylight saving time in 2022 with the exception of Baja California and certain border municipalities that still follow the US schedule. The Ukrainian parliament voted in 2024 to cancel daylight saving time, so Ukrainians will skip the change for the first time in spring 2025.