ASU Sleep Scientist Megan Petrov Explains Why Permanent Standard Time Beats Permanent Daylight Saving Time

Twice a year, most Americans surrender an hour of sleep in the spring and reclaim it in the fall, a ritual that has sparked growing frustration among lawmakers and the public alike. Congress is once again weighing whether to end the semiannual clock change altogether. Arizona State University sleep scientist Megan Petrov, an associate professor in ASU’s Edson College of Nursing and Health Innovation, believes lawmakers are asking the right question but leaning toward the wrong answer. According to Petrov, the goal should not be permanent daylight saving time but permanent standard time, because it aligns far better with human biology. This article breaks down the science behind that position, examines who stands to lose the most under a year-round daylight saving schedule, and offers practical, evidence-based guidance for protecting your sleep during any time transition.

The Choice Before Congress: Two Ways to Stop Changing the Clocks

The national conversation about clock changes is often muddled by a persistent misconception: that daylight saving time gives us more daylight. It does not. The number of daylight hours in any given day is fixed by the Earth’s tilt and orbit. What daylight saving time does is shift one hour of usable daylight from the morning to the evening. That single fact sits at the center of Petrov’s argument, and understanding it is essential to evaluating the policy options now on the table.

What Permanent Daylight Saving Time Would Look Like

Under permanent daylight saving time, the country would stay on its spring-and-summer schedule all year. Clocks would read one hour ahead of the sun relative to standard time. The practical effect: later sunrises and later sunsets. Workers and students would gain an extra hour of light after school or work, an appealing prospect for shopping, dining, recreation, and outdoor activity, which is precisely why the policy attracts strong commercial and public support.

The trade-off arrives every single morning. Darker mornings mean many people would wake up, commute, and send children to school before sunrise for extended stretches of the year. And because human bodies depend on morning light to set their internal clocks, that trade-off carries real biological consequences that marketing campaigns for extra evening light rarely mention.

What Permanent Standard Time Would Look Like

Permanent standard time keeps clocks synchronized more closely with the sun’s natural position. Sunrises come earlier, and sunsets come earlier. Arizona already operates on permanent standard time, with the exception of the Navajo Nation, and residents there never experience the jolt of springing forward or falling back. There is no transition week, no spike in groggy commuters, and no annual disruption to household routines.

For Petrov, this arrangement is preferable for one central reason: permanent standard time aligns the clock on the wall with the clock inside the human body. Want to understand how sleep and circadian research informs health policy and clinical practice? Explore the work being done at ASU’s Edson College of Nursing and Health Innovation, where researchers study sleep and circadian rhythms across the human lifespan.

Morning Light and Circadian Rhythms: The Biology Behind the Debate

The human body runs on circadian rhythms, internal clocks that regulate sleep, hormone release, metabolism, body temperature, and countless other essential processes. These rhythms do not run on wall-clock time. They run on sunlight, and morning light in particular plays a critical role in keeping them synchronized.

When morning light reaches the eyes shortly after waking, it signals the brain’s master clock to begin the day’s cascade of biological timing: alertness hormones rise, metabolic processes align with activity, and roughly fourteen to sixteen hours later, the body is primed for sleep at a biologically appropriate hour. When that morning light signal is delayed because the sun rises later, as it would under permanent daylight saving time, the entire system shifts later with it. People struggle to wake, feel groggy through the morning, and often cannot fall asleep earlier at night because their internal clock has been pushed back too.

Petrov puts it plainly: our bodies need morning light to synchronize our body clocks so that our bodily systems can function on a regular rhythm. Evening light, by contrast, pushes the biological clock in the opposite direction, delaying sleep onset and shortening total sleep time, especially for people whose schedules are fixed by external demands such as school and work start times. While a later sunset may sound attractive to consumers, it is not what human physiology needs to operate at its best.

Who Pays the Price Under Permanent Daylight Saving Time?

The costs of a poorly aligned clock are not distributed evenly across the population. Petrov identifies several groups that would bear a disproportionate burden if the country locked in daylight saving time permanently.

Teenagers and Students

Adolescents may be the most vulnerable group of all. During puberty, natural biological changes shift teens’ internal clocks later, making them inclined to fall asleep and wake later than children or adults. Layer chronic sleep deprivation on top of that, which is already common among high school students juggling early start times, homework, jobs, and screens, and the problem compounds.

Under permanent daylight saving time, more evening light would push teen bedtimes even later. School start times, however, would not move. As Petrov notes, students still have to get up for school and still have to get there on time. The result: more students commuting in the dark and arriving at class with even less sleep than they get now, undermining learning, focus, memory consolidation, and academic performance across an entire generation of learners.

Older Adults and People With Existing Health Risks

Older adults often experience age-related shifts in sleep timing and quality, making them more sensitive to misalignment between their internal clocks and the demands of the day. People with cardiovascular vulnerabilities face additional risk. Heart attacks and strokes are more likely to occur in the morning hours, and research has associated the sleep loss triggered by the spring transition with elevated cardiac events. A policy that chronically shortens and delays sleep on a national scale would likely amplify these risks rather than reduce them.

Morning Commuters

Dark mornings also carry a straightforward safety cost. Traffic accidents rise in the days following the spring clock change, and permanent daylight saving time would place more commuters on dark roads every morning for extended portions of the year, particularly in winter months when even standard time sunrises come late. Pedestrians, cyclists, and school-age children walking to bus stops would share that increased exposure.

Preparing for Seasonal Clock Changes: Practical Steps From Sleep Science

Until policymakers settle the debate, most Americans will continue to face the spring and fall transitions each year. Petrov offers evidence-based strategies to soften the blow:

• Adjust gradually. In the days leading up to a time change, shift your bedtime and wake time by fifteen to twenty minutes per day in the direction of the coming change. A slow transition gives your circadian system time to adapt rather than shocking it overnight.
• Prioritize morning light. The single most powerful tool for resetting your internal clock is bright light exposure shortly after waking. Open the curtains, step outside, or take a morning walk. Morning light, Petrov says, will wake you up more quickly and help you function at your best.
• Protect your evening routine. Dim household lights and limit screen use in the hour or two before bed so you do not counteract the morning light signal you worked to establish.
• Guard sleep duration during the transition week. Treat the days after a clock change as a recovery period: keep schedules consistent, avoid late caffeine, and resist the temptation to correct your schedule with drastically different weekend sleep patterns.

Have questions about how the time change affects your household? Share your experience in the comments below, especially if you are a parent, teacher, or shift worker navigating early mornings on behalf of others.

Sleep as a Public Health Issue, Not Just a Policy Preference

Petrov is careful to frame the daylight saving debate as more than an economic or lifestyle question. Proponents of permanent daylight saving time often point to the consumer benefits of an extra evening hour: more shopping, more restaurant visits, more outdoor recreation, more spending. She does not dismiss those interests, but she insists they come with a bill attached.

That cost will still be paid, she argues, and it will not produce a national net benefit. Chronic misalignment between social time and biological time contributes to insufficient sleep, poorer health outcomes, reduced workplace and academic performance, and preventable safety incidents. Those costs are harder to see on a balance sheet, but they are paid in emergency rooms, classrooms, and on roadways.

Sleep, she argues, deserves the same policy seriousness as nutrition or physical activity. Sleep is universally important, Petrov emphasizes, because it is vital for memory, for making sound decisions for our families and ourselves, and for long-term health. Treating an hour of morning light as disposable overlooks how foundational that light is to every system in the body.

The Bottom Line: Choose the Time That Matches Human Biology

The debate before Congress ultimately comes down to a simple question: should the nation’s clocks serve commerce or biology? Petrov’s answer, grounded in years of research on sleep and circadian rhythms, is unambiguous. Ending the twice-yearly clock change is a worthwhile goal, but the end state matters. Permanent standard time keeps morning light where the human body expects it, protects the sleep of children and teenagers, and reduces health and safety risks for everyone.

For readers, the immediate takeaways are practical. Use morning light deliberately. Adjust gradually before each transition. Treat sleep as a pillar of health rather than a luxury. And when the policy debate reaches another vote, remember that the question is not whether an hour of daylight exists. It is where that hour does the most good.

Found this analysis useful? Share it with parents, educators, and commuters in your network, and explore our related articles on sleep health and healthy living for further reading.

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