Why do we still change clocks? Daylight saving vs. standard time

Locking the Clock

Mara: On July 14th, 2026, the House passed a bill from Florida congressman Vern Buchanan. It's called the Sunshine Protection Act. That same day, in words posted by the House Energy and Commerce Committee, Buchanan turned to the other chamber: 'I urge the Senate to send this long-overdue reform to the president's desk.' The reform is simple to say. Daylight saving time, made permanent, nationwide. Any state that wants out has to opt out before it takes effect.

Eli: And the listener who wrote in wants to know two things. Is turning the clocks back actually bad for health? And why doesn't anyone just pick one time and stick with it?

Mara: Buchanan's bill is one answer to that second question. Whether it's a healthy answer is another matter. Lock the clock anywhere, and somebody's winter day starts or ends in the dark. Today's angle is the fatal flaw of winter morning darkness.

Eli: Lock it to summer time, then. The spring-forward hour just never gets handed back.

Mara: Right. No falling back in November, ever. Lighter evenings all year, darker winter mornings. Buchanan says it would promote healthier, more active lifestyles.

Eli: And on paper he has the country with him. A 2025 AP-NORC poll had 56% of Americans backing permanent daylight saving. Standard time got 42. So people mostly agree on locking the clock, and split over which clock. States have moved too. Nineteen have passed trigger laws, set to switch to permanent daylight saving the moment Washington allows it. And Washington has to allow it. Under the Uniform Time Act of 1966, a state can stay on standard time all year. Staying on summer time takes an act of Congress.

Mara: So nineteen states have passed laws that, for now, do nothing at all.

Eli: And notice what that poll asks about, Mara: a clock. The people fighting this bill aren't arguing about a clock. They're arguing about a December sunrise.

The Autumn Paradox

Mara: Before the sunrise, the hour itself. Spring takes one away. Autumn hands it back. The clocks go back, daylight saving ends, and anyone who goes to bed at the usual time that night gets an extra hour of sleep.

Eli: An hour lost in spring, an hour returned in autumn. Sounds like a mirror image.

Mara: It isn't. Melanie de Lange and colleagues went through English health records from 2008 to 2019. They looked at acute cardiovascular events, the sudden ones, heart attacks and the like, in the week after the clocks went back. The rate dipped. Around fifty a day per region before. Just under forty-nine after. Small, but down, not up. For them, autumn looks largely benign, even protective, next to spring.

Eli: Not everyone reads that autumn week as good news, though.

Mara: No. In those English records, recorded depression dipped that week too. But the American Academy of Sleep Medicine points to Denmark. Across its psychiatric hospitals, the incidence rate of unipolar depression rose 11% after the autumn change. The academy's reading starts in the evening. The clocks go back and the dark arrives an hour earlier, at the end of the working day. Losing that evening light can hit mood hard. Sometimes it's the opening of seasonal affective disorder, a depression tied to a lack of sunlight.

Eli: Same season, and the mood data points in opposite directions.

Mara: And there's a smaller, very physical risk. Insulin pumps don't adjust themselves for the clock change. Someone has to reset them. One nurse practitioner, updating her own pump for daylight saving, swapped the a.m. and p.m. settings. Hours later her blood sugar began to rise. She'd been getting less insulin during the day than she needed. She caught it before bed, and avoided a dangerous low overnight.

Eli: Clinicians at Michigan State have seen those dosing errors after both changes, spring and autumn.

Mara: She and her co-authors closed their paper hoping the public would back laws to abolish daylight saving nationwide. Abolish it. Buchanan's bill would keep it, all year round.

Morning Sun vs. Evening Spend

Eli: Here's the machinery underneath. The body runs on a master clock, a circadian rhythm that tells it when it's day and when it's night. This clock runs a little longer than twenty-four hours. Left alone, it drifts later. So it needs a nudge every single day to stay in step with the sun, and that nudge is morning light. As Jamie Zeitzer at Stanford puts it, light in the morning speeds the circadian cycle up. Light in the evening slows it down. Standard time, he says, puts more light early in the day, which keeps that clock robust.

Mara: So morning light isn't a nicety. It's the daily reset button.

Eli: Which is where the sleep doctors line up. Muhammad Rishi led the American Academy of Sleep Medicine's 2024 position paper, and he puts it flatly: 'permanent standard time is the best option from a human biology standpoint.' Daylight saving shifts the clock on the wall an hour ahead of the sun, so the morning reset comes later. That chronic gap between the body's clock and the social one is called social jet lag. Over recent decades, studies have linked it to shorter sleep, type 2 diabetes, obesity and heart disease.

Mara: And that hour ahead is exactly what Buchanan's bill would lock in, every day of the year. Whether the Senate ever moves it is still unknown.

Eli: Rishi says there's no evidence the body ever fully adapts to living an hour off the local sun.

Mara: Rick Scott, who calls it his Sunshine Protection Act, sees that same hour as a gift: 'For many Americans, an extra hour of daylight means more time to play outside with their kids, walk their dog, or spend time with neighbors.' That's the recreation case. Daylight after work becomes time outdoors, with family and neighbors.

Eli: And there's money in that hour. The JPMorgan Chase Institute compared Los Angeles with Phoenix, where clocks don't change. Card spending is the trace it followed, every swipe at a register. When daylight saving ended, daily card spending in Los Angeles fell 3.5% relative to Phoenix. The sharpest weekday drops came at grocery stores, gas stations, retail and discount shops. The after-work errand, basically.

Mara: So the biology wants that light in the morning, and the cash registers want it in the evening. Same hour, two claims on it.

Eli: And a law can only hand that hour to one side, Mara. Give it to the evening, and in December the walk to the bus stop happens before sunrise.

The Winter Disaster of 1974

Mara: That commute has been tried. Winter, 1974. An oil embargo, and Congress passes an emergency energy law. Virtually the whole country goes onto daylight saving time on January 6th. A winter lived on the summer clock. Children walk to school and wait for buses before sunrise. The National Bureau of Standards found a statistically significant rise in morning traffic deaths among school-age children. In Florida, eight schoolchildren died in traffic accidents. Florida's governor called the legislature into special session and proposed going straight back to Eastern Standard Time for most of the state.

Eli: So Buchanan's bill isn't a new idea. The country already ran it.

Mara: Ran it, and dropped it fast. One TV commentator said daylight saving in the winter 'has proven to be Daylight Disaster Time.' People disliked the dark mornings, the evaluations found little energy or safety benefit, and by that November the country was back on standard time.

Eli: And the arithmetic is hard to beat. One urban economist worked out the commute trade. A dark evening commute would have to be five to seven times as dangerous as a dark morning one for daylight saving to be the safer clock. That's the deadlock: some commute gets the dark either way, and the morning one is far harder to offset. He also says the safety differences are small and shouldn't drive the decision. Meanwhile the morning dark lands on the very hour the body uses for its reset.

Mara: That winter still gets cited in Congress. In the House Rules Committee, Pennsylvania Democrat Mary Gay Scanlon said it was 'repealed within a year because it didn't work.' She told colleagues to weigh 'the extra hours of darkness in the winter.'

Gridlock on the Hill and Abroad

Eli: That warning still echoes in the Senate. When the House passed Buchanan's bill, it wasn't close: 308 to 117. It went through over the objections of medical groups and lawmakers from Midwestern states. President Trump has called for permanent daylight saving too. The next day, the bill went to the Senate Commerce Committee. And there it sits. That's what stalled means here: not voted down, just not taken up.

Mara: Medical groups and the Midwest. The same dark-morning worry, fifty years on.

Eli: In October 2026, the Senate Majority Leader was asked about it. 'The President feels strongly on it like he does a lot of issues,' he said. 'It's something we're having conversations about, but there's no clear path forward or consensus on it yet.'

Mara: Rishi lives in Indiana, and he makes the worry concrete. With winter daylight saving, he says, 'the sun would not come up in Indianapolis until after 9 A.M. My kids' school starts around 7:15 in the morning.'

Eli: At least two hours of school before sunrise, by his count. Zeitzer's team at Stanford took the question to the whole population. They built a model, a simulation running people's body clocks through each option. In Zeitzer's words, 'staying in standard time or staying in daylight saving time is definitely better than switching twice a year.' But the options aren't equal. Locked on standard time, they estimate, the country would avoid some 300,000 strokes a year. Locked on summer time, it would get about two-thirds of that gain.

Mara: Europe knows this argument well. Back in the 1990s, Portugal tried the time Spain and France use. Winter sunrises came too late, people complained, and Portugal went back. A Spanish historian calls it 'a lesson in prudence for the Peninsula.' He also says Europe's trouble 'isn't Brussels, but the lack of coordination between states.'

Eli: So it's a neighbor problem as much as a sunrise problem.

Mara: On both sides of the Atlantic, the objection that keeps coming back is a late winter sunrise.

Why We Keep Switching

Eli: Europe even got further than Washington. In a 2018 EU-wide consultation, 84% of respondents wanted the seasonal change ended. The European Parliament voted the next year to end it, starting in 2021. Without agreement among member states, it never happened. In the US, the choice comes in three: summer time for good, standard time for good, or the switch as it is. One sleep specialist points out the appeal of the third: it spares politicians a choice that's very hard to make. That's the stalemate. Nearly everyone wants the switching gone, and no single time serves both the morning and the evening.

Mara: So, the health half. For the heart, the week of the extra hour looks largely protective: the English records show those events dipping. On mood, the evidence splits: English records dipped, Danish hospital visits rose.

Eli: And the second: nobody picks one time because each choice has a loser. The summer clock puts children back where they stood in the winter of 1974, waiting for buses in the dark. The standard clock takes evening light from the shoppers, the parks and the bill's backers. So the country keeps the switch it's tired of.

Mara: Signals to watch: a first hearing or vote on Buchanan's bill, any consensus in the Senate or the European Council, and new studies weighing autumn's heart benefit against its toll on mood.

Eli: One thing to explore is the 1974 winter daylight trial.

Mara: Follow politics as lawmakers weigh permanent clock changes against public health concerns.

Eli: Thanks for listening. I'm Eli.

Mara: And I'm Mara. Until next time.