Permanent daylight time harms sleep

A CMAJ analysis argues that choosing permanent daylight saving time (rather than permanent standard time) shifts winter sunrises later by about an hour in many Canadian cities, meaning more commutes and school starts occur before sunrise. That reduced morning light weakens circadian entrainment and raises risks for sleep problems, seasonal depression and reduced learning or productivity for early‑schedule groups. — This reframes a seemingly technical clock decision as a public‑health policy choice that affects schooling, mental health, and labor productivity across regions and seasons.