Governments considering an end to twice‑yearly clock changes should favour permanent standard time if they wish to protect public health, researchers say. While cancelling the spring and autumn shifts eliminates the immediate disruption associated with the clock change, the longer‑term consequences depend on which time is kept year‑round.
Morning light and the body clock
An analysis led by Raymond Lam, professor of psychiatry at the University of British Columbia, argues that morning daylight is critical for synchronising human circadian rhythms. The research team notes that choosing permanent daylight saving time—which keeps evenings lighter—also delays sunrise by an hour in winter, so more people wake and travel in darkness.
"Ending the clock change solves one problem, but it creates another decision: which time should we live on year‑round?" said Raymond Lam, the lead author of the analysis.
Ralph Mistlberger, professor of psychology at Simon Fraser University, explained the mechanism driving the recommendation. He said our biological clocks need exposure to morning light to stay aligned with the 24‑hour day, and that shifting morning light later into the day undermines that alignment—particularly during dark winter months.
Health trade‑offs: short‑term disruption versus chronic misalignment
The seasonal clock change itself has recognised short‑term effects on sleep, mood and accident risk, particularly after the spring forward. Removing the changes would remove those acute impacts, but the analysis emphasises that the permanent choice determines chronic outcomes.
Permanent standard time preserves earlier dawns during winter months and therefore maintains morning light that helps reduce sleepiness, supports sleep quality and stabilises mood. By contrast, permanent daylight saving time provides later‑evening light that can benefit social and economic activity but at the cost of later morning light and greater circadian misalignment for many people.
- Permanent standard time: aligns better with physiological needs; preserves morning light that synchronises circadian rhythms.
- Permanent daylight saving time: offers lighter evenings favourable for recreation and some economic activity but delays sunrise and increases the number of people commuting in darkness.
- Keeping clock changes: retains twice‑annual disruption with acute health and safety effects, especially in spring.
Policy implications for South Africa
Although the analysis focuses on the biological evidence rather than specific national legislatures, its conclusions are directly pertinent to policymakers weighing whether to abolish seasonal clock adjustments. If the primary aim is to protect population sleep and mental health, the evidence presented by Lam and colleagues favours adopting standard time throughout the year.
Decision‑makers must balance that health evidence against social and economic considerations. The analysis notes the attractiveness of lighter evenings for leisure, retail and commuting patterns, but underscores that those benefits come with measurable costs to circadian alignment and long‑term wellbeing when morning light is reduced.
What the analysis does not change
The researchers are not arguing merely to stop changing clocks; they are asking societies to make an informed choice about which permanent time to adopt. Ending biannual shifts addresses immediate harms, but it is not an end of the debate: choosing permanent daylight saving time or standard time will shape chronic public health outcomes for years.
| Option | Main benefit | Main drawback |
|---|---|---|
| Permanent standard time | Better circadian alignment from morning light | Earlier dark evenings in summer |
| Permanent daylight saving time | Lighter evenings for social and economic activity | Later sunrises and increased morning darkness |
| Keep seasonal changes | Maintains traditional clock arrangements | Repeated short‑term sleep and safety impacts |
For citizens and legislators aiming to translate scientific evidence into policy, the key question is whether evening light or morning light should be prioritised when the clock is fixed. The analysis makes clear that, from a biological and public‑health perspective, morning light carries greater weight.
