Across much of the United States and Canada, daylight saving time begins Sunday at 2:00 a.m. local time. Most people will turn their clocks forward an hour, trading an hour of sunlight in the mornings for more daylight at the end of the day. When it ends, clocks will turn backward by an hour nearly eight months later to have more morning light in the darkest days of winter.
But British Columbia will switch their clocks for the last time — ushering in a new era of permanent daylight saving time. The switch was supported by “more than 90% of British Columbians,” said David Eby, premier of British Columbia.
“The way that we live our lives now in the modern era, having an extra hour of sunlight at the end of the day, whether it’s the winter or the summer, makes a big difference for people,” Eby told NPR’s Adrian Ma on All Things Considered.
While the idea may be popular among British Columbia residents, experts in sleep medicine and public health caution against permanent daylight saving time.
“Daylight saving time has been shown to have a lot of negative effects,” said Emily Manoogian, a senior staff scientist at the Salk Institute and an executive member of the Center for Circadian Biology at University of California, San Diego. She noted that the United States once tried permanent daylight saving in the 1970s and quickly reversed course after people were commuting and children were going to school in the dark, and there were a few fatal car accidents.
Eby acknowledged health risks but said people in his province are accustomed to dark winter mornings. “We’re on the very western edge of the time zone and so we have dark mornings anyway,” he said. “People really want that hour at the end of the day.”
Why daylight saving is bad for our bodies
Our biology favors permanent standard time because internal circadian clocks — which govern sleep-wake cycles and many cardiac and metabolic functions — are synchronized to daylight, Manoogian explained. Light is the largest cue that coordinates behavior: when eyes detect sunlight upon waking, they signal the brain to alert the body it’s daytime. Without morning light, the body can struggle to wake, and bright evenings make it harder to fall asleep. That can shift bedtimes later and make mornings harder, impairing daytime cognition and metabolic functioning.
These disruptions have public health consequences. Studies have linked the start of daylight saving time to short-term increases in car accidents, heart attacks and strokes. “Sleeping, eating, getting light at the wrong time is a huge risk for cardiometabolic disease,” Manoogian said. She added that scientific and medical societies generally argue against switching to daylight saving time, noting the policy was originally intended to save energy — a benefit research has not substantiated.
A study by Stanford researchers published in the Proceedings of the National Academy of Sciences found that switching clocks twice a year takes a substantial public health toll, increasing strokes and obesity. The study estimated that permanent standard time would result in 300,000 fewer strokes and more than 2 million fewer cases of obesity compared with the current practice. Permanent daylight saving also reduced strokes and obesity but to a lesser extent than permanent standard time.
“When we can realign better to our environment, we get better sleep,” Manoogian said. “We have lower risks of almost any chronic disease you can imagine — cardio-metabolic, cancer, even depression, bipolar disorder.” She summarized that the health benefits of standard time are considerable.
Soften the blow of time change on your body
If you’re concerned about how daylight saving time might affect you and your family, Manoogian suggests ways to ease the transition:
– Get enough light in the mornings: If the sun is out when you wake, go outside or ensure bright light indoors. If it’s dark, turn on many lights to simulate daylight.
– Prioritize sufficient sleep: Adults generally need seven to nine hours. Consistency in sleep duration is important.
– Maintain consistent meal times: Eating during the part of the day when you’re active can improve metabolism. Waiting an hour or two after waking to eat and confining meals to an 8–10 hour window can lower measures like HbA1c and improve metabolic health.
– Ease kids into the shift: Move bedtimes and wake times gradually, such as by 20 minutes a day over several days, to help children adjust.