How Daylight Saving Time Affects Your Sleep (and How to Adjust)
Changing the clocks shifts your daily schedule by an hour, but your body clock doesn’t move with it straight away. The spring change, when you lose an hour, is the harder one: a study of 22 years of US data found fatal car crashes rise about 6% in the week after clocks spring forward. The fall change is usually easier, but it can still disturb sleep for several days.
Key facts
- In the US and most of Canada, clocks go back 1 hour on Sunday, November 1, 2026, and forward on Sunday, March 14, 2027.
- British Columbia, Alberta and Manitoba no longer change their clocks.
- Fatal crashes rose about 6% in the week after the spring change in a study of US data from 1996 to 2017.
- The American Academy of Sleep Medicine supports ending clock changes and adopting permanent standard time.
What the clock change does to your body
Your body clock (circadian rhythm) is set mainly by daylight, especially morning light. When the clocks spring forward, your alarm goes off an hour earlier by your body’s reckoning, and mornings are darker again. Most people lose sleep for a few nights and feel more tired until their body clock catches up, which can take several days.
When the clocks fall back, you get an extra hour in bed and lighter mornings, which suits the body clock better. But you may wake up earlier than you want, and evenings get dark an hour sooner.
What the research shows
- Road crashes: Josef Fritz, Céline Vetter and colleagues analysed 732,835 fatal crashes in the US from 1996 to 2017. In the week after the spring change, fatal crashes rose about 6%. The effect was stronger, over 8%, in places on the western edge of their time zone, where mornings are darkest.
- Health: The American Academy of Sleep Medicine (AASM) says the switch to daylight saving time creates a mismatch between the body clock and the social clock, which carries risks for physical and mental health and safety.
Permanent daylight time or permanent standard time?
Many people want to stop changing the clocks, but there’s disagreement about which time to keep.
- Permanent standard time is supported by the AASM and many sleep scientists. They argue it best matches human biology, because it gives more light in the morning, which keeps the body clock in step.
- Permanent daylight time gives lighter evenings, which supporters say is better for business, outdoor activity and evening road safety.
In 2026, British Columbia, Alberta and Manitoba chose permanent daylight time and won’t turn their clocks back on November 1. In the US, the House of Representatives passed a bill for permanent daylight time in July 2026, but it hasn’t passed the Senate. Our sister site ClockNow explains where Canada and the US stand and lists every clock change until the end of 2027.
How to adjust to the fall clock change
When the clocks go back, your body will want to wake up an hour earlier than the new clock time. To ease into it:
| Night | Bedtime (if you normally go to bed at 10:30 PM) |
|---|---|
| Thursday | 10:45 PM |
| Friday | 11:00 PM |
| Saturday | 11:15 PM, then the clocks go back |
| Sunday onwards | 10:30 PM on the new time |
- Get outside in daylight on Sunday afternoon and early evening.
- Keep your alarm at your usual time on the new clock from Monday.
How to adjust to the spring clock change
Spring is harder because you lose an hour. Shift your schedule earlier by 15 to 20 minutes a night for 3 or 4 nights before the change, and get bright light as soon as you can after waking for the first few days afterwards. Be extra careful driving on the Monday morning.
Use the sleep calculator to pick a new bedtime that gives you enough sleep for your alarm.
Sources
- Fritz J et al. A chronobiological evaluation of the acute effects of daylight saving time on traffic accident risk. Current Biology, 2020. Summary: Sleep Review
- Rishi MA et al. Permanent standard time is the optimal choice for health and safety: an American Academy of Sleep Medicine position statement. Journal of Clinical Sleep Medicine, 2024
Frequently asked questions
Do we gain or lose sleep in November?
You gain an hour on the night the clocks go back, though many people find themselves waking an hour early for a few days.
How long does it take to adjust to the time change?
Usually a few days to a week. Morning light helps your body clock adjust faster.
Why is springing forward worse?
You lose an hour of sleep, and mornings suddenly become darker, which makes it harder for your body clock to adjust.
