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 a popular one among British Columbia residents, experts in sleep medicine and public health are not fans of the time change.
"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. "And actually the United States tried permanent daylight savings in the seventies for one year. It was so awful that they reverted it almost immediately."
People went to work in the dark and children walked to school in the dark. And then, "there were a few fatal car accidents," she said, which led to the reversal.
Eby acknowledged health risks, but added that people in his province are used to waking up in the dark and taking their kids to school in the dark during the winter.
"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
While our modern world and lifestyles may favor permanent daylight saving, our biology supports a permanent standard time. That's because our internal circadian clocks — which control not just our sleep-wake cycle, but also our cardiac and metabolic pathways — are synced to daylight, according to Manoogian.
"Light is the largest cue to coordinate behavior," she said. When we wake up and our eyes detect sunlight, they send a signal to the brain to tell the rest of the body to wake up and gear up for the day.
"So when you're not getting light in the morning, your body thinks it's not morning yet," she explained. "And it's very hard to just force your body to wake up without that light."
Similarly, in the evenings, when it's bright outside, our bodies find it harder to go to sleep. And it's easy to get stuck in a cycle of later bedtimes and a tougher time waking up in the mornings. That cycle can affect our cognitive functioning during the day and our metabolism all day long. This has widespread public health impacts, said Manoogian. It can also lead to more car accidents, heart attacks and strokes in the week following the start of daylight saving time.
"We know that sleeping, eating, getting light at the wrong time is a huge risk for cardiometabolic disease," said Manoogian. "Every medical and scientific society would argue we should never go to daylight saving time. It was originally created to try to save energy, [but] evidence has shown it does not save energy."
A study by Stanford researchers published in the Proceedings of the National Academy of Sciences in September 2025 found that switching our clocks twice a year takes a massive public health toll, primarily by driving up the number of strokes and cases of obesity per year. It also found that switching permanently to standard time would result in 300,000 fewer people having strokes and more than 2 million fewer cases of obesity.
"When we can realign better to our environment, we get better sleep," said Manoogian. "We have lower risks of almost any chronic disease you can imagine — cardio-metabolic, cancer, even depression, bipolar disorder."
The Stanford researchers also found that permanent daylight saving reduced the number of strokes and obesity, but less so than permanent standard time. In other words, as Manoogian puts it, "the health benefits of standard time are pretty great."
Soften the blow of time change on your body
If you're concerned about how daylight saving time might affect your and your family's health, Manoogian has some tips to soften the transition on your body.
- Get enough light in the mornings: If the sun is out when you wake up, make sure you get enough light, said Manoogian. If it's dark when you wake up, at least turn on as many nights in your home as possible.
- Prioritize getting enough sleep: Seven to nine hours of sleep is considered ideal for adults, with some people needing closer to seven and others needing closer to nine hours. You know what your body needs, so make sure you get that. "Consistency is also key," said Manoogian. So try and get the same amount of sleep every night.
- Have consistent meal times: "Keeping a consistent eating pattern to the part of the day when you're active and best able to process food, can have dramatic health benefits," she said. That might mean waiting an hour or two after you wake up to eat breakfast and keeping all meals to within an 8-10 hour window. "It can decrease Hb1C, which is kind of the gold standard for measuring blood glucose," she says. "It also is shown to decrease cholesterol in animal studies. It's shown to increase health span and even lifespan."
- Ease kids into the time shift: "Usually what we do for our family is we try to shift like 20 minutes a day over like three days," said Manoogian, who has two children. "That can go a long way" toward helping kids' bodies to adjust to the shift forward.
Copyright 2026 NPR
