Canada's patchwork of time zones creates health concerns for winter

This weekend marks a new divergence in timekeeping across Canada as several provinces have ended the practice of changing clocks twice a year. British Columbia, Alberta, Manitoba and the Northwest Territories will now observe permanent daylight time, joining Yukon and Saskatchewan. Residents of most of Ontario, Quebec and the Atlantic provinces will still turn their clocks back one hour on Nov. 1. Quebec Premier Paul St-Pierre Plamondon announced his government intends to abolish the time change, with this weekend likely being the last switch, though the province has not yet decided whether to keep standard or daylight time permanently.

Which provinces have stopped changing their clocks?

The provinces ending seasonal time changes this year are most of British Columbia, Alberta, Manitoba and the Northwest Territories. They have all chosen to keep daylight time year-round. Saskatchewan has not changed its clocks since 1966, and Yukon made its change permanent in 2020. In northwestern Ontario, some regions will also maintain daylight time to align with Manitoba. Ontario passed legislation in 2020 to make daylight time permanent, but it has not yet taken effect, pending coordination with neighbouring jurisdictions. Quebec plans to hold a short parliamentary commission to consult experts before making its final decision.

What are the health concerns with permanent daylight time?

Scientific analysis favours permanent standard time over daylight time for health reasons, as it better aligns with the body's natural rhythm. Michael Antle, a University of Calgary psychology professor, said permanent standard time would have been better for Alberta, given its northern latitude and already late winter sunrises. "It's not the choice I would have made," he said of the province's decision. Antle explained that permanent daylight time means society agrees to start the day an hour earlier, which can create a mismatch with the body's internal clock, especially when morning light arrives later. He cited studies linking later sunsets to less sleep and higher rates of obesity, diabetes and heart disease.

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How does the spring time change affect health?

The shift to daylight saving time in spring is particularly disruptive because it cuts an hour of sleep, creating an abrupt mismatch between the body's clock and solar time. Joseph De Koninck, an emeritus professor of psychology at the University of Ottawa, said our biological clock uses light to synchronize itself and struggles with a sudden one-hour adjustment. "We are able to adapt, but it's not optimal for our health," De Koninck said. Michael Antle noted the spring change can leave people feeling out of sync for weeks. De Koninck warned that prolonged sleep disruption from such mismatches can lead to a host of psychological and physical issues.

What will researchers study in Canada's new time patchwork?

The country's emerging time zone patchwork presents a natural experiment for scientists to study populations living under different systems. Researchers plan to examine impacts on mental health, traffic collisions, and school and workplace performance. Michael Antle said he wished for baseline data collection before Alberta's change. Joseph De Koninck noted modern tools allow for detailed tracking of sleep habits over time to compare adaptation between provinces. However, he expects public reaction in Western Canada may surface before long-term studies are complete, as people experience darker winter mornings. "Those who've tried it haven't liked it," De Koninck said.

With files from CBC News