Permanent Standard Time May Be Better for Canadian Health Than Year-Round Daylight Saving Time
Canadian health researchers are urging governments to choose permanent standard time over permanent daylight saving time if twice-yearly clock changes are abolished, warning that darker winter mornings could negatively affect sleep, mental health, learning and productivity.
As Canadian provinces consider whether to end twice-yearly clock changes, researchers argue that permanent standard time is better for public health than keeping daylight saving time year-round. Image credit: ChadoNihi.
Why researchers favour permanent standard time
Several jurisdictions in Canada have moved to permanent daylight saving time after eliminating seasonal clock changes.
Yukon adopted the policy in 2020, followed by British Columbia in March 2026 and Alberta and the Northwest Territories a month later.
The U.S. House of Representatives also passed legislation in July that would make daylight saving time permanent nationwide, although the bill remains in the Senate.
“Stopping changing our clocks solves one problem, but it requires another decision: what time of day should we live throughout the year?” said study lead author Raymond Lamb, a professor at the University of British Columbia.
“Health evidence points to standard time, primarily because morning light is important for our body clock, sleep and mood.”
Professor Lamb and his colleagues examined the health implications of two possible permanent systems rather than the broader question of whether seasonal clock changes should be abolished.
The researchers concluded that accumulating evidence supports permanent standard time because it more closely aligns the clock with human circadian biology.
How permanent daylight saving time would affect winter mornings
The difference becomes especially important during the winter months. Permanent daylight saving time would delay sunrise by one hour compared with permanent standard time.
For example, in Toronto, the latest winter sunrise would occur at 8:51 a.m. under permanent daylight saving time, compared with 7:51 a.m. under permanent standard time. In Calgary, the corresponding times would be 9:40 a.m. and 8:40 a.m.
An additional hour of morning darkness could mean that people travel to work or school before sunrise, while daylight would shift into the evening.
This change could affect sleep, mood, learning and productivity, particularly for people who already experience sleep problems or follow an early schedule. The researchers say the reason is linked to the body’s circadian clock.
“Our body clock needs morning light to stay in sync with the 24-hour day,” said study co-author Ralph Mistleberger, a professor at Simon Fraser University.
“Permanent daylight saving time would shift winter morning light one hour later, when mornings are already the darkest.”
Potential effects on seasonal depression and mental health
The analysis also highlights concerns about seasonal depression.
An estimated 1–3% of Canadians experience seasonal affective disorder, while as many as 15% experience milder seasonal changes in mood, sleep, appetite and energy.
Seasonal depression is common during Canadian winters. Symptoms such as low energy, lack of sleep and difficulty concentrating can be especially noticeable in young people.
Morning bright-light therapy is an evidence-based treatment for seasonal affective disorder. By delaying natural morning light, permanent daylight saving time could work in the opposite direction by weakening important circadian signals.
Drawbacks of permanent standard time
The researchers acknowledge that permanent standard time would also have disadvantages.
Earlier summer sunrises could create problems for people who tend to wake early, while earlier winter sunsets could limit outdoor and commercial activities in the evening.
They recommend relatively modest measures to reduce these effects, including blackout curtains and public education about sleep health.
Measures needed if daylight saving time becomes permanent
By contrast, permanent daylight saving time would require a broader range of measures to reduce the effects of darker winter mornings.
- Improved street lighting and sidewalks
- Enhanced road-safety measures
- Reflective devices for children
- Later school start times
- Flexible work schedules
- More morning lighting in schools and workplaces
Clinicians could also prepare to monitor patients for sleep disturbances and seasonal mood symptoms.
The scientists advised governments to closely track the effects of whichever system is chosen, including school absences, mental health and sleep problems, workplace and road accidents, physical activity and cardiovascular events.
They also called for data to be examined by age, geography, socioeconomic status, locality and exposure to shift work so that unequal impacts are not overlooked.
Balancing brighter evenings with morning health
“The appeal of permanent daylight saving time is easy to understand,” said co-author Patrick Bayliss, a researcher at the University of British Columbia.
“People like brighter spaces after work or school.”
“However, these nighttime benefits need to be weighed against evidence that later solar time reduces sleep, reduces productivity and worsens educational outcomes.”
The paper was published in the Canadian Medical Association Journal.
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Raymond W. Lamb et al. 2026. Analyzing the health impacts of implementing permanent standard time or permanent daylight saving time to inform Canadian policy. CMAJ 198 (34): E1335–E1340. doi: 10.1503/cmaj.261089
Source: www.sci.news