The Clock-Change Debate: Why Sleep Scientists Back Permanent Standard Time

Almost everyone agrees on one thing about changing the clocks twice a year: we're tired of it. Polls consistently find that a large majority of Americans want to stop the biannual ritual of springing forward and falling back. The disruption is real, and the spring shift in particular, when we lose an hour of sleep, is linked to a measurable spike in heart attacks, strokes, and car crashes in the days that follow.

So when a bill lands in Congress to end the clock changes for good, and the nation's sleep physicians line up behind it, that seems like a straightforward good-news story. But there's a twist that most people miss, and it's the whole crux of the debate. Ending the clock changes means picking one time to keep permanently, and the choice between the two options, permanent standard time and permanent daylight saving time, is not a coin flip. Sleep and circadian scientists have a clear and strongly held preference, and it's probably the opposite of what most people would guess. Here's what's happening, and why the science points where it does.

What the bill actually does

In July 2026, Representatives Mary Gay Scanlon of Pennsylvania and Pat Harrigan of North Carolina introduced the Sunshine for Our Kids Act (H.R. 9638), a bipartisan bill that would make standard time permanent across the United States, ending daylight saving time nationwide ^{[1, 2]}. Mechanically, it repeals the daylight saving time provision of the longstanding Uniform Time Act, while preserving a path for individual states to opt into daylight saving time if they choose, provided the whole state observes the same time ^[2].

The American Academy of Sleep Medicine (AASM), the professional body for sleep physicians, has publicly celebrated the bill's introduction and thrown its support behind it, along with the broader Coalition for Permanent Standard Time ^[1]. That endorsement isn't casual, it reflects a formal position the AASM has held for years, grounded in circadian biology. And the name of the bill is a tell: the "for Our Kids" framing points squarely at one of the central arguments, children's safety and school performance during dark winter mornings.

The part most people get backwards

Here's the crux. When people imagine ending the clock changes, many instinctively want to "lock in" summer's long, bright evenings, and that would be permanent daylight saving time. It sounds appealing: more daylight after work, later sunsets year-round, no more dark 5 p.m. winters.

But sleep scientists overwhelmingly favor the other option, permanent standard time, and understanding why requires one key insight: your body's internal clock is set primarily by morning light, not evening light ^{[3, 4]}. Light in the morning is one of the most powerful signals for synchronizing your circadian rhythm; it tells your brain it's time to be awake and alert, and it anchors the timing of everything downstream, including when you'll naturally feel sleepy that night. Evening light does the opposite, it delays your clock and suppresses melatonin, the hormone that signals sleep ^[4].

Daylight saving time shifts an hour of daylight from the morning to the evening. And here's the thing the "more daylight" framing obscures: it doesn't create any additional daylight. The total is exactly the same; the hour just gets moved from morning to evening ^[5]. So permanent daylight saving time would take away morning light, precisely when your body most needs it, and add it to the evening, precisely when extra light works against your sleep.

The consequences of permanent DST would be most stark in winter. Under permanent daylight saving time, many parts of the country wouldn't see sunrise until well after 8 a.m., and some northern areas would approach 9 a.m. sunrises ^{[3, 6]}. That means millions of people, and crucially millions of children heading to school, waking and commuting in complete darkness for months. That's both a circadian problem (bodies struggling to wake without morning light) and a safety problem (kids traveling to school in the dark), and it's the specific scenario the "for Our Kids" bill is designed to avoid.

Why morning light matters so much

To see why this hour matters so much, it helps to understand how your circadian rhythm works, the roughly 24-hour internal clock that sets not just your sleep timing but your metabolism, hormones, and cardiovascular rhythm.

It's worth pausing on the biology, because it's the foundation of the whole scientific position. Humans evolved under the sun, and our internal clocks are calibrated to it. Morning light exposure does several things at once: it sets the circadian clock early in the day, promotes daytime alertness and better mood, and, by anchoring the clock earlier, helps you fall asleep at a reasonable hour that night ^[4]. When sunrise comes later, as it would under permanent DST, people wake further from their natural light cues, and over time their sleep and circadian rhythms get pushed later, which research links to shorter sleep and poorer health outcomes ^[4]. This is the same mechanism at work in shift work and circadian rhythm sleep disorders, where the clock and the schedule fall out of step.

This is also why the school angle carries real weight. Adolescents already have biologically later circadian rhythms, which is why so many communities have moved to later school start times. Permanent daylight saving time would work against that, making dark winter mornings even harder for students to wake, learn, and travel safely ^{[3, 4]}. Standard time, by keeping clock time closer to solar time, keeps morning light where the body can use it.

The honest other side

In the spirit of a fair account, permanent daylight saving time isn't irrational, it simply optimizes for different values. Its supporters point to genuine benefits: longer bright evenings that encourage outdoor recreation, exercise, shopping, and dining, and fewer gloomy pre-5 p.m. winter sunsets ^[6]. Those are real quality-of-life preferences, and some of the arguments for permanent DST are rooted in economic behavior and lifestyle rather than health ^[7].

The important distinction is that the case for permanent standard time is primarily about circadian health and safety, while much of the case for permanent daylight saving time is about evening lifestyle and commerce. Reasonable people can weigh those differently. But when the question is narrowed specifically to sleep, health, and safety, which is the lens sleep medicine applies, the evidence points consistently in one direction. As the AASM and numerous sleep scientists have concluded, from a health perspective, permanent standard time is the better choice ^{[1, 5]}.

One more point of near-universal agreement worth emphasizing: whatever time we land on, most experts agree that ending the twice-yearly switch itself is valuable, because the transitions, especially the spring "spring forward," are when the documented harms cluster ^{[5, 7]}. The debate is about the destination, not about whether to stop changing the clocks.

What this means for you, regardless of what Congress does

Legislation moves slowly, and whether this bill becomes law is uncertain. But the underlying science is immediately useful no matter what the clocks say, because it points to something you control: your own light exposure.

The single most actionable takeaway is to prioritize morning light. Getting bright light, ideally sunlight, soon after you wake helps set your circadian rhythm, boosts daytime alertness, and supports better sleep that night, exactly the mechanism at the heart of the standard-time argument. This matters even more in winter and on dark mornings. Conversely, dimming lights and limiting screens in the hour before bed protects the evening wind-down that bright light would disrupt. And keeping a consistent sleep and wake schedule, including through the clock changes while they still exist, cushions your body against the disruption. If you want the practical version of all of this, our guide to getting more deep and REM sleep walks through what actually works.

In other words, the same principle driving the policy debate, morning light aligns your clock and evening light delays it, is one you can act on tonight, regardless of what Congress decides.

The bottom line

The Sunshine for Our Kids Act reflects a growing consensus that the twice-yearly clock change should end, and the sleep medicine community strongly supports it. But the science adds a crucial wrinkle most people find surprising: of the two ways to stop changing the clocks, permanent standard time is the one aligned with human biology, because it preserves the morning light your circadian rhythm depends on, while permanent daylight saving time would push winter sunrises dangerously late and rob your body of that morning signal. The appeal of endless bright evenings is understandable, but from the standpoint of sleep, health, and children's safety, the experts are clear. And whatever happens in Congress, the lesson is one you can use now: chase the morning light, protect the evening dark, and your internal clock will thank you. If you are exhausted no matter how well you manage your light and your schedule, that deserves a closer look, because fatigue can point to a breathing problem during sleep.

Frequently asked questions

This article is for general education and isn't a substitute for individual medical advice, nor a political endorsement. It summarizes the position of sleep-medicine organizations on the health science of time policy.