Daylight saving time will end this weekend, much to the dismay of people who dread ending their workday in darkness. Some dislike the change so much that they want to make DST permanent – as legislation that passed the House in July and has President Donald Trump’s support would do.
On the surface, this might sound like a great idea. Who wouldn’t want more afternoon sunlight? But it would be terrible for people’s health, which is why many major medical organizations oppose it, including the American Academy of Sleep Medicine, American Academy of Neurology and American Medical Association. Instead, they advocate keeping standard time in place year-round.
To understand why, see how the different time-change scenarios affect Americans’ daily routines:
Notice that with year-round DST, many more Americans would be waking up in the dark and going to school and work before sunrise. That might benefit recreational activities done later in the day, which is why the golf industry is a prominent proponent of making DST permanent. But it goes against human’s natural circadian rhythms, which rely on morning light to set internal clocks and regulate sleep-wake cycles.
In fact, exposure to daylight later in the evening “tends to keep us awake and delay when we wake up the next morning,” said Erik Herzog, a circadian biology researcher at Washington University in St. Louis.
Advocates for permanent DST are not wrong to want to end the biannual time change, which substantially disrupts people’s circadian rhythms. Multiple studies have documented increases in car crashes, heart attacks and workplace accidents, including medical errors, in the days following the time change. The spring transition is particularly disruptive because people lose an hour of sleep, which explains why a 2025 poll found that just 12 percent of Americans favor the current system.
The problem is that year-round DST would further deprive people of morning sunlight, especially during the winter months, when days are already short. A 2026 analysis of the nation’s 100 largest school districts found that if the policy were implemented, students in 94 of them would have to travel to school in darkness. In areas along the western edges of time zones, the sun would not rise until after 9 a.m on some days.
A new study in the journal Cell Biology estimated that year-round DST would result in more than 2 billion additional school commutes before sunrise each year. That’s concerning because children between the ages of 5 and 18 are more than twice as likely to die from pedestrian-vehicle collisions before sunrise as they are after. In fact, the United States already tried permanent DST in 1974 and abandoned it partly due to public outrage over schoolchildren killed while waiting in the dark at bus stops.
A wealth of research has also linked the transition to DST with other health risks, including heart rhythm abnormalities, strokes, obesity, diabetes and seasonal depression. Scientists have even found found higher rates of several cancers, including breast cancer and melanoma, among people living in the western portions of time zones with later sunrises.
“As soon as you switch into the next time zone as you’re moving west, suddenly the people living right next door seem to have lower rates of cancer,” Herzog said.
So what’s the best solution? The consensus among medical experts is that prioritizing daylight in the morning over the afternoon is paramount. That makes permanent standard time the best choice. The next best option would be to retain the twice-yearly clock changes but shorten the time in DST.
“The worst choice is permanent daylight saving time,” said Vishesh Kapur, a sleep medicine physician at University of Washington. That’s because it would create year-round misalignment between our biological clocks and the daylight cycle, he argued.
Arizona, Hawaii and all U.S. territories already observe standard time year-round, as do more than 60 percent of countries worldwide. U.S. lawmakers appear divided. Nineteen states have approved permanent DST, but many state bills also favor standard time. The federal bill that passed the House, the Sunshine Protection Act, has attracted bipartisan support, but so has a competing bill, the Sunshine for Our Kids Act, that would make standard time the national default.
As lawmakers weigh these options, they should consider what’s more important: an extra hour of golf after work, or safer children and a healthier population. As with all public health decisions, science can and should inform the debate, but the ultimate choice comes down to societal values.
Have questions or comments about daylight saving time? Please write to me. I will feature reader responses in a future edition of The Checkup newsletter.
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