On July 14, 2026, the House of Representatives passed the Sunshine Protection Act of 2025 by a vote of 308-117, a bipartisan bill that would make daylight saving time permanent nationwide. The measure has President Trump's backing and now heads to the Senate, where its fate remains uncertain. A similar bill passed the Senate in 2022 but was never taken up in the House. The end of twice-yearly clock changes is broadly popular. The debate over which time to make permanent is not.
Changing the clocks twice a year is a documented health hazard.
The biannual spring-forward has a measurable toll. When Americans lose an hour of sleep in March, rates of heart attacks rise in the days immediately following the transition. A meta-analysis of multiple epidemiological studies found an increased risk of acute myocardial infarction following the spring shift that does not appear after the fall transition. Finnish researchers reported an 8% rise in ischemic stroke in the first two days after the spring change. Sleep researchers attribute these acute effects to a combination of sleep deprivation, disrupted circadian rhythms, and the resulting activation of inflammatory and cardiovascular stress pathways.
On this point, there is strong scientific consensus: the current system is the worst option.
Where the experts and Congress diverge is over which permanent time is better.
In September 2025, researchers at Stanford Medicine published a study in the Proceedings of the National Academy of Sciences that modeled the long-term circadian and health consequences of all three time policy options: permanent daylight saving time, permanent standard time, and the current biannual switching. It is the most data-grounded analysis of this question to date.
The finding: permanent standard time benefits the most people. By prioritizing morning light, standard time aligns more closely with what circadian biology actually needs. "When you get light in the morning, it speeds up the circadian cycle. When you get light in the evening, it slows things down," said Dr. Jamie Zeitzer, professor of psychiatry and behavioral sciences at Stanford and senior author of the study. "You generally need more morning light and less evening light to keep well synchronized to a 24-hour day."
The researchers estimate that permanent standard time would result in approximately 300,000 fewer strokes and 2.6 million fewer cases of obesity nationwide compared to the current system. Permanent daylight saving time -- the option Congress just passed -- would deliver roughly two-thirds of that benefit.
The American Academy of Sleep Medicine, the American Medical Association, and the National Sleep Foundation all endorse permanent standard time.
The organizations representing sleep medicine and public health are aligned on this. The argument for permanent standard time comes down to light timing and circadian synchronization. The human circadian cycle runs slightly longer than 24 hours for most people, and morning light is what corrects it each day. Evening light does the opposite -- it extends the cycle further, pushing sleep later and making it harder for the body to run on the 24-hour schedule the world demands.
Permanent daylight saving time means darker mornings throughout the winter in exchange for brighter evenings. In some parts of the country, the sun would not rise until after 9 a.m. under the new system -- a concern that derailed a similar proposal in the 1970s, when a 1974 trial of permanent daylight saving time was abandoned in less than a year after public opposition, including from parents of children going to school in the dark.
This is a circadian health issue, and circadian health touches almost everything.
At AB, we spend a lot of time talking about what goes into the body. But when the body functions is just as important. Circadian rhythm regulates hormone production, metabolic rate, immune signaling, insulin sensitivity, cortisol timing, and appetite. Chronic circadian misalignment -- the kind produced by persistent light exposure at the wrong time -- is associated with elevated risk of obesity, metabolic syndrome, diabetes, and cardiovascular disease. These are not fringe concerns. They are the documented downstream effects of living out of sync with your biology.
Congress passed a bill that would stop the biannual disruption. That is a real improvement. But the bill also locks in a time system that keeps morning darker than it needs to be, shifting millions of people toward greater circadian burden. The science says we could do better.
