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Making daylight saving time permanent would mean losing sleep — and lives

This legislation is not about protecting sunshine. Instead, it should be called ‘An Act to Force Americans to Wake Up an Hour Earlier Each Day.’

Capitol Hill in Washington on March 15, 2022. Senator Marco Rubio of Florida reintroduced legislation that would end the practice of turning clocks back one hour every November. SARAHBETH MANEY/NYT

On March 2, Senator Marco Rubio reintroduced legislation that the Senate unanimously approved by voice vote in 2022 without a single public hearing. The Sunshine Protection Act, which would permanently move standard time one hour earlier in states that currently observe daylight saving time, could increase the danger to kids going to school, damage the mental health of all Americans, and mess with our body clocks. The bill would legislatively move our clocks one time zone to the east, requiring Americans to wake up an hour earlier each day relative to sunrise, the equivalent of permanently setting your alarm an hour earlier. States on the West Coast would change their clocks to what is now Mountain Standard Time, Mountain Standard Time in Denver would move to Chicago’s Central Standard Time, and Chicago would permanently move to New York City’s Eastern Standard Time.

This nationwide change would be permanent. No more seasonal falling back or springing forward. This legislation is not about protecting sunshine. Instead, it should be called “An Act to Force Americans to Wake Up an Hour Earlier Each Day.”


The timing of exposure to sunlight each day is the human reset button for our internal circadian clocks, which regulate our ability to consolidate sleep and wakefulness and impact many aspects of body and mental function. The legislation would permanently create less morning light exposure. Less morning light is associated with depression and would also impact the safety of tens of millions of schoolchildren as they go to school largely in the dark. Yes, daylight saving time gives us those long evenings of sunlight, but for the human body and our internal circadian clocks, that late-day sunlight is too late and not enough to give our bodies and brains the reset that morning sun provides.

Studies have shown that people sleep less during daylight saving time because they are exposed to more light at later hours, which pushes their internal circadian clocks later. When the alarm rings under a permanent daylight saving time, we wake earlier than our brain’s circadian clock, cutting sleep short. Insufficient sleep is a nationwide problem that has already been linked to increased rates of diabetes, mood disorders, errors and accidents, and impaired learning and driving, especially for sleepy adolescents .


And on the western edge of any time zone, people are already sleeping less without this radical change — especially people with children and jobs that start work before 7 a.m., which disproportionately affects those who earn lower wages and come from disadvantaged backgrounds. Overall, wages also decrease by 3 percent in the western edge of a time zone compared to the eastern edge of that same time zone .

Living on the western edge of a time zone also significantly increases the risk of some types of cancer, cardiovascular disease, and diabetes. Data suggest that advancing the nation’s clocks eastward as mandated by the Sunshine Protection Act could eventually cause up to an additional 100,000 cancer cases per year , including 5 percent to 10 percent more breast cancer cases and 15 percent to 30 percent more uterine cancer, liver cancer, and chronic lymphocytic leukemia cases.

In the end, while the legislation is couched in language that dreamily offers more daylight to Americans (which Congress cannot provide), the likely outcome would significantly degrade public health and safety. Congress should commission the National Academy of Science to conduct a study on the health, safety, economic, and other implications of moving our clocks one hour later. Our children and families deserve to know how the so-called benefits compare to the dire drawbacks.


Dr. Charles A. Czeisler cofounded and directs the Division of Sleep Medicine at Harvard Medical School, where he is the Frank Baldino Jr. PhD Professor of Sleep Medicine and a professor of sleep medicine. He teaches undergraduate courses at Harvard College and is founding chief of the Division of Sleep and Circadian Disorders at Brigham and Women’s Hospital. Dr. Elizabeth B. Klerman is a professor of neurology at Massachusetts General Hospital and Harvard Medical School.