By Anne Engel, NBC-HWC · Building Healthspan · Sleep & Recovery
The short answer: your body clock sets itself by light and routine, not by the clock on the wall. To reset after daylight saving time, keep a steady wake-up time (even on weekends), get outside for morning light, and dim the lights in the evening. Research suggests that sleeping on a regular schedule may matter as much as, or more than, how many hours you sleep.
Key takeaways
Your internal clock responds to light and routine, so a consistent wake-up time is one of the most useful sleep habits.
In a UK study of about 60,000 adults, more regular sleep timing was a stronger predictor of lower mortality risk than sleep duration.
Ordinary room light before bed delayed melatonin and shortened the body's biological night by about 90 minutes compared with dim light.
Think of sleep as having two bookends: a steady morning and a soft, dim evening.
The extra hour I didn't get
The Saturday the clocks fell back, we hosted a big Halloween block party. I got to bed around 11, looking forward to that rare extra hour of sleep.
Then I was wide awake at 5am. The clock said 5am. My body said 6am. Both were right.
My body didn't care what the clock said. It knew exactly when I usually wake up. After years of working on a consistent schedule, that early wake-up was actually a good sign.
Why do I wake up so early after the clocks fall back?
Your body runs on an internal (circadian) clock that cues hormones, body temperature, appetite and sleepiness. It doesn't read the clock on your microwave. It reads light and your routine. When the clocks fall back an hour, your body keeps its old schedule for a few days, so a 6 a.m. body wake-up shows up as 5 a.m. on the clock.
Is a consistent sleep schedule more important than sleeping longer?
For years, my pattern was the familiar one: up early all week for work, then trying to catch up on the weekend. Over the last few years I've switched to protecting the same hours instead of chasing more of them. I get up around the same time every morning, weekends included.
The research supports this. In a study published in the journal Sleep, researchers calculated sleep regularity for about 60,000 UK Biobank participants, average age 63, using a week of activity-tracker data. People with the most regular sleep schedules had a lower risk of death over the following years than those with the least regular schedules, and regularity was a stronger predictor than sleep duration. It's an observational study, so it shows a link rather than cause and effect, but it points to consistency as a simple target.
Does dim light in the evening really help you sleep?
Evening light was the part that surprised me most. In a study from Brigham and Women's Hospital and Harvard Medical School, people exposed to ordinary room light before bedtime started producing melatonin later, and their melatonin "night" was about 90 minutes shorter than when they were in dim light.
I've become the lamp person in my house. My family teases me, but after a while in softer evenings, a bright kitchen at 9 p.m. feels jarring. It's like noticing which foods don't agree with you once you start paying attention.
A few things I do:
Switch from overhead lights to lamps after dinner.
Brush my teeth by a side light instead of the bathroom overhead.
Put my phone and laptop away a couple of hours before bed.
Read something light and easy before sleep.
The sleep bookends: a simple way to reset your body clock.
I think of these habits as bookends. A steady morning on one side, a soft evening on the other, with sleep in between.
After my 4 a.m. wake-up, I was ready for bed early the next night and slept straight through until my alarm at 5:50. One short night, and my body found its way back. I call this Practice the Return: we all drift with time changes, travel and late nights, and the bookends make the return faster.
Pick one to try this week:
Morning light: step outside within an hour of waking, even for five minutes. A gray sky is still brighter than indoor light.
Steady wake-up time: keep it within about an hour on weekends.
Softer evenings: lamps instead of overheads after dinner.
Gentler bedtime: a side light for your nighttime routine.
Quieter mind: put your phone down 30 minutes earlier than usual.
Frequently asked questions
How long does it take to adjust to the time change?
Most people adjust within a few days to a week. Keeping your usual wake-up time and getting morning light helps your body catch up faster.
Is it bad to sleep in on weekends?An occasional lie-in is fine. But regularly sleeping much later on weekends shifts your body clock, which can make Monday mornings harder. Aim to keep your wake-up time within about an hour.
What counts as dim light in the evening?
Think lamps and side lights rather than bright overhead lighting, especially in the last couple of hours before bed.
Can I still get morning light on a cloudy day?
Yes. Even an overcast sky is typically much brighter than indoor lighting, so a few minutes outside still counts.
Your next step
Which end of your day is harder to protect, the morning or the evening? Start there. Sleep is one of the 8 Roots of Healthy Aging, and small, steady habits here support energy, mood and long-term health.
Get the free Sleep Bookends Guide: a one-page guide to steady mornings and soft evenings, with a 7-day tracker.
It comes with Building Healthspan, my Thursday note with one simple idea for building your future health.
Sources
Windred DP, et al. Sleep regularity is a stronger predictor of mortality risk than sleep duration: a prospective cohort study. Sleep. 2024;47(1):zsad253.
Gooley JJ, et al. Exposure to room light before bedtime suppresses melatonin onset and shortens melatonin duration in humans. Journal of Clinical Endocrinology & Metabolism. 2011;96(3):E463–E472.
Anne Engel is a National Board-Certified Health & Wellness Coach and former Fortune 50 marketing executive who helps midlife women build strength, energy and confidence for the decades ahead. This post is for education only and isn't medical advice.
