If you’ve ever felt a little “off” after the clocks change, you’re not imagining it. Daylight saving time (DST) is a policy in which clocks shift forward by one hour in spring and back again in autumn. Standard time tracks the sun more closely (think: solar noon near 12 pm).
DST pushes daily life “later,” as sleep gets trimmed and mornings shift darker, which can scramble the body’s internal timing and is associated with increased rates of cancer, obesity, heart attacks, diabetes, suicide, and motor vehicle incidents [1, 2, 3, 4, 5]. The literature increasingly supports sticking with standard time year-round for better alignment with human biology [6, 7].
Why your body cares: Circadian rhythms 101
Circadian rhythms are 24-hour biological cycles that regulate the entire functioning of the human body. This includes the body’s production of hormones that regulate sleep, hunger, and metabolism. Ultimately, these rhythms regulate your body weight, performance, mood, and susceptibility to disease. Changing your rhythms throws off your body’s timetable. This not only affects sleep, but any organ and bodily function can be compromised by a disrupted circadian rhythm [8, 9, 10, 11].
Light is the primary cue for the master clock in your brain, which is why the timing and spectrum of light matter big time and why darkness is necessary for nighttime biology [12]. Food intake and movement are secondary cues for the clocks in our gut and muscles [13, 14]. Ideally, light, movement, food, and temperature signals are in sync within your body and with your environment for optimal functioning [15]. When the social clock (work, school, screens) diverges from the sun clock (light and dark), misalignment creeps in and it also interferes with the seasonal adjustment of our body clock [16, 17].
DST is similar to “social jet lag”
Losing or gaining an hour may sound small, but your circadian system moves in increments, not leaps. The spring shift especially creates a mismatch — later evening light and darker mornings. A single-hour change can echo for days in how you feel and function [18, 19].
Scientists call this kind of mismatch “social jet lag” (SJL) — the difference between your body clock and the social clock. A perfect example of SJL is sleeping in on the weekends. SJL is a classical circadian disruption and is linked with higher health risks over time, including metabolic issues, obesity, diabetes, cardiovascular problems, and mood issues [20, 21, 22, 23, 24]. DST increases the discrepancy between the sun clock and the social clock and therefore increases the discrepancy between your body clock and the social clock, enforcing social jet lag on everyone [16].
How to cushion the next clock change
1) If you can, live by the sun — not the clock.
The gold standard is to anchor your schedule to the sun: rise near sunrise, get bright daylight after waking, and make your nights darker. This isn’t feasible for everyone, but the closer you get, the steadier your circadian timing and health. Set your wake time relative to the sun with the app “Circadian: Your Natural Rhythm” and optimize your daily flow.
2) Pre-shift your schedule by 15 minutes.
Four days before the DST change, move bedtime and wake time by ~15 minutes each day. Do the same with meals, caffeine, workouts, and light exposure. On change day, your body only has to bridge a small leftover gap.
3) Increase daytime and reduce evening light exposure
To facilitate a better and more rapid adaptation to DST, increase your natural light exposure during the day, especially in the morning, while increasing brightness and overall light exposure in the evening/night [19]. This is a key circadian health hack for life, not just for DST.
4) Drive and decide defensively.
In the week after the spring change, build in an extra buffer for commutes, and be mindful of fatigue-related slips in attention and reaction time [25, 26].
Optimize circadian rhythms & natural health (year-round)
1) Prioritize natural morning light.
Get outside first thing after waking for at least 10 minutes (even on overcast or rainy days). Natural morning light is the single most powerful signal to set your master clock, wake you up by boosting cortisol, shut down melatonin release, and improve your sleep the coming night [27, 28, 29].
2) Minimize and mitigate artificial light at night.
Use warm, circadian-friendly lighting, dim light sources, reduce brightness, and use nighttime blue light blocking glasses (orange/red lenses) after nightfall, and especially 1-2 hours before bed. This way, you protect your master clock from getting the wrong time cue, as well as protecting your cortisol/melatonin rhythm, your sleep, and the alignment of countless body clocks downstream of the brain [30, 31, 32, 33, 34].
3) Keep sleep/wake times steady—weekends included.
Avoid big swings in schedule (“Saturday sleep-ins”) that drive social jet lag and circadian disruption [35, 36, 37]. Aim for a regular sleep window you can stick to every day.
4) Time your meals and stimulants.
Have a hearty breakfast within a couple of hours of rising and finish eating 3-4 hrs before bed [38, 39, 40, 41]. Have coffee with or after breakfast, then cut caffeine by early afternoon to protect both sleep and your clock. [42, 43]. This will support your sleep, metabolism, and nighttime repair activities.
5) Move—especially earlier.
Daytime activity reinforces your “day” signal and morning training can help you fall asleep earlier. [44, 45]. If you exercise at night, keep it moderate and finish at least 1-2 hours before bed [46, 47].
The bottom line
Your circadian system is exquisitely tuned to the light–dark cycle. When we push society “later” with DST or ping-pong our schedules on weekends, we burden our biology and invite more dis-ease. The evidence now leans toward standard time year-round as the healthiest default. You can protect your rhythm by stacking powerful daily cues—morning light, steady schedules, earlier dinners, and darker evenings. Do these consistently to feel better and be healthier. If you can arrange your schedule to be more driven by sun-time vs social-time, your body won’t even notice the next clock shift.
Resources
If you want to learn more about circadian rhythms and how to optimize your health through a more aligned lifestyle, download the app “Circadian: Your Natural Rhythm” and check out these guides:
