Should Daylight Saving Time be abolished? It’s almost time for North America to “fall back” as DST ends this weekend. The clocks will be set back one hour at 2 a.m. (to 1 a.m.) local time on Sunday, Nov. 2, 2025, according to Timeanddate.com.
As a result, people will gain an hour on the clock, with the biggest consequence being an extra hour in bed this Sunday. Sunrise and sunset will be an hour earlier, with more light in the morning and less in the evening. Those working night shifts — and pet owners — may find the adjustment more disruptive. However, according to new research by Stanford Medicine scientists, changing clocks twice a year has unhealthy consequences for all.
What Is Daylight Saving Time?
It’s the period between March and November, with November to March known as standard time (ST). The concept is that switching to DST brings more daylight in the evening in the summer.
DST begins on the second Sunday in March (when clocks are set forward one hour at 2 a.m.) and ends on the first Sunday in November (when clocks are set backward one hour at 2 a.m.).
DST does not apply in Arizona (except in the Navajo Nation) and Hawaii, as well as in the U.S. territories of American Samoa, Guam, the Northern Mariana Islands, Puerto Rico, and the U.S. Virgin Islands.
Is Daylight Saving Time Bad For Health?
The researchers of a study published in September in the Proceedings of the National Academy of Sciences estimate that permanent standard time would prevent about 300,000 cases of stroke per year and result in 2.6 million fewer people having obesity, while permanent daylight saving time would achieve about two-thirds of the same effect. However, it’s the twice-per-year swap between ST and DST (called Biannual Shifting or BAS) that has the most negative effects. “We found that staying in standard time or staying in daylight saving time is definitely better than switching twice a year,” said Jamie Zeitzer, a professor of psychiatry and behavioral sciences at Stanford University and senior author of the report.
According to the Sleep Foundation, switching to DST each March is disruptive and can cause upticks in heart problems, mood disorders and motor vehicle collisions. Humans’ circadian rhythms have a 24-hour cycle, which is regulated by exposure to natural light.
Standard Time Vs. Daylight Saving Time
A Gallup survey earlier this year found that 72% of Americans want no clock changes, with 48% wanting permanent standard time and 24% wanting permanent DST. Just 19% want to maintain the current system.
Arguments for permanent daylight saving time: Those in favor of using permanent daylight saving time argue that more evening light can save energy, reduce crime and give people more leisure time after work. However, children have to walk to school in the dark.
Arguments for permanent standard time: Proponents of using permanent standard time think it’s healthier to have more light in the morning. Standard time is also the default time for in an astronomical sense. It aligns more closely with the sun’s position, with solar noon occurs closer to 12 p.m.
What The Data Says About DST
The data reveals an answer. “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 Zeitzer. “You generally need more morning light and less evening light to keep well synchronized to a 24-hour day.” The researchers found that over an entire year, the circadian burden is reduced under permanent standard time, which prioritizes morning light.
Is that the argument settled? No, because the study assumed that people have a steady sleep schedule and spend time outdoors before and after work and indoor light exposure from 9 a.m. to 5 p.m. The reality, however, is likely very different. “People’s light habits are probably much worse than what we assume in the models,” said Zeitzer. “Even in California, where the weather is great, people spend less than 5% of their day outside.”
Wishing you clear skies and wide eyes.