The science explains the fog—and gives fixes.
As the clocks change, a small tweak in time can rattle routines that felt solid yesterday. You notice odd hunger pangs, a flat mood, clumsy moments and a nagging urge to nap. Once you grasp what that 60-minute nudge does to the body’s timekeepers, the whole week starts to make sense.
What a 60-minute shift does inside your body
Your body runs on a circadian system tuned to a little over 24 hours, anchored by light. A cluster of neurons in the hypothalamus—the suprachiasmatic nucleus—acts as the master clock. Special cells in the eye send it a “light now” signal, which sets the schedule for hormones, sleep pressure, digestion, temperature and alertness.
Change the clock and you send mixed messages. Morning arrives on the wall, but your biology still thinks it is the old time. Melatonin lingers, so you feel groggy. The cortisol awakening surge shifts, so you feel flat at 9am then oddly keyed-up late afternoon. Your core temperature minimum slides, so your coordination and reaction times dip at unusual hours.
Most bodies re-align by about 20–40 minutes per day. A one-hour clock change usually needs 3–5 days to settle.
That lag creates the “little jet lag” people notice in late October and late March. In the autumn switch, evenings darken early and many people yawn after dinner. In the spring switch, you lose sleep and wake in the dark, which cuts alertness on the first workday.
The clock in your brain, and the ones in your organs
The brain’s master clock leads, but your heart, liver, gut and muscles keep their own time too. Food, movement and temperature cue these peripheral clocks. If you push mealtimes back but keep snacking late, your liver lags. If you scroll under bright screens at 23:00, your eyes tell your brain it’s earlier than it is. The result is a drift between clocks, felt as broken sleep, cravings and uneven energy.
Morning light advances your body time. Evening light delays it. That simple rule explains why a brisk walk at 08:00 helps more than a sleepy lamp at 20:30. It also explains why a bright kitchen at night can keep you up, even when you feel worn out.
Common symptoms you can expect
People report a similar cluster of effects in the first week after the switch. Not everyone gets them all, but the pattern is recognisable.
- Difficulty falling asleep, or waking too early for several days.
- Dip in focus mid-morning, then a slump mid-afternoon.
- Stronger cravings for quick carbohydrates at unusual times.
- Short fuse, lower motivation and reduced patience.
- Worsening of migraines or anxiety in sensitive individuals.
Three powerful levers reset your clock: morning light, regular meals and a stable wake-up time.
Who feels it most
Anyone can feel off, but some groups carry more risk.
- Children: their clocks adapt more slowly to imposed schedules. Expect early waking or bedtime protests for a few nights.
- Teenagers: late chronotypes struggle with earlier mornings; school performance can dip for a short spell.
- Older adults: sleep becomes lighter with age; the shift can mean more night-time waking and a higher fall risk at dawn.
- Shift workers: already misaligned clocks magnify the effect of the change.
- People with mood disorders or migraines: rhythm disruption can trigger symptoms.
- Those at higher latitudes: large seasonal swings in daylight add another stressor.
A seven‑day plan to regain your rhythm
Start small adjustments before the change, then lock in a simple routine after it. Tiny steps accumulate quickly.
| Day | Wake time | Bedtime | Light and habits |
|---|---|---|---|
| −3 days | Shift by 15 min | Shift by 15 min | 20–30 min outdoor light within an hour of waking |
| −2 days | Shift by another 15 min | Shift by another 15 min | Keep dinner at least 3 hours before bed |
| −1 day | Shift by another 15 min | Shift by another 15 min | Reduce caffeine after 14:00; dim lights after 21:00 |
| Change day | Wake at the new time | Stick to target bedtime | Morning light; avoid long naps; gentle exercise |
Three quick rules that make the biggest difference
- Anchor wake-up time: get up at the same clock time daily, even if sleep felt patchy.
- Front‑load light: go outside within one hour of waking; keep evenings dim and screen‑light low.
- Regular meals: eat breakfast soon after waking; finish dinner earlier for a few nights.
Add supportive tactics: keep the bedroom cool (around 18°C), plan a brisk walk at lunch, and swap intense late‑evening workouts for earlier sessions. If you nap, set a 20–25 minute timer before 15:00.
Risks and what the numbers say
Sleep loss and darker commutes shift risk in measurable ways. Large datasets in Europe and North America link the spring clock change to a small rise—often 5–10%—in heart attack admissions on the following Monday. Road collision risk rises when evening darkness arrives suddenly after the autumn shift. Fatigue, slower reaction times and reduced visibility stack the odds against drivers and pedestrians.
You can act to lower your personal risk. Keep the first working day lighter if you can. Avoid high‑stakes decisions before lunch. Take extra care on the roads at dusk. Cyclists and walkers benefit from high‑visibility gear for the first fortnight.
Should the clock change stay?
Energy savings from shifting the clock now look modest with modern lighting and heating. Public health bodies point to better sleep, safer evenings and more stable routines under a permanent standard time aligned to solar noon. Others argue for a later clock to stretch usable light after work. The best compromise depends on geography, commuting patterns and how schools and businesses schedule their days.
Across Europe the discussion continues. Many health experts favour scrapping seasonal changes. Employers and schools already test flexible starts in winter, which eases the strain without a legal overhaul. The direction of travel seems clear: fewer forced jumps, more daylight‑aware planning.
Helpful add‑ons you can use this week
Social jet lag, in plain terms
When your weekend schedule drifts from your weekday schedule by 2 hours or more, you build “social jet lag”. The clock change magnifies it. Reduce the gap over the next two weekends by waking within 60–90 minutes of your workday alarm and keeping meal times steady.
A simple home simulation
Set an alarm 15 minutes earlier each day for four days before the switch. Expose your eyes to daylight within an hour of waking. Move dinner earlier by 15–30 minutes on the same days. This simulation teaches your body to expect the new timing before it arrives.
Medication and training timing
Time‑sensitive medicines—blood pressure tablets, insulin, ADHD medication—should shift gradually. Move doses by 15 minutes per day over 3–4 days rather than by a full hour at once. Athletes can protect performance by scheduling key sessions at the new competition time during the week after the change.
Family and care tips
- Children: bring bath and story time forward by 10–15 minutes from mid‑week; reduce evening screen exposure.
- Older adults: keep corridors lit at dawn; plan balances and strength exercises earlier in the day; review fall‑risk medicines.
- Pets: adjust feeding windows in 10–15 minute steps; pets cue strongly to food time and will adapt smoothly.
Morning light advances, evening light delays. Use that rule and the one-hour shift stops feeling like a mystery.
The body reads reliable signals. Give it daylight early, meals on time and a steady wake time, and that “lost or gained hour” becomes a short, manageable adjustment rather than a week‑long drag.
