Clocks Gone Back? How to Reset Your Body Clock for Darker Evenings

Why the clocks going back can leave you out of sync

Your body runs on an internal clock, often called your circadian rhythm. It decides when you feel sleepy and when you feel alert, and it keeps to a cycle of roughly 24 hours. In the early hours of Sunday, the clock on the wall jumped back an hour. Your body clock did not.

So for the first few days, your body is running an hour ahead of the new time. At 9pm it feels like 10pm, which is why you may feel sleepy earlier than usual. At 6am it feels like 7am, which is why so many people wake before the alarm. Darker evenings add to the effect: when the sun sets before you have finished work, the evening can feel later than it is.

The main signal that keeps your body clock in step with the day is light. A review of the science describes ambient light as the most important time cue the brain's master clock receives. Daylight reaching your eyes tells your brain what time it is, and your clock gradually shifts to match. That is why light timing matters so much this week, and why the adjustment takes days rather than minutes.

What happened to the extra hour?

The autumn change is often described as a free hour in bed. A review of the research on clock changes found little evidence that people actually sleep longer on the night itself. Many people then wake earlier for several days in a row, so the week as a whole can end up with less sleep, not more. If you feel tired despite the extra hour, that is a common pattern, not a sign that something is wrong.

How long does it take to adjust?

For most people, a few days to about a week. Each steady wake-up time and each spell of daylight nudges your body clock a little closer to the new time.

The autumn change is usually the easier of the two. A study run under carefully controlled lighting found that the average human body clock runs slightly longer than 24 hours, at about 24 hours and 11 minutes. Because it tends to run a little long, most people find it easier to drift later, which is what the autumn change asks of you, than to jump earlier, as the spring change does.

How much you notice it depends on your natural timing:

• Early risers often feel it most. If you usually wake at 6.30am, your body may now wake you at 5.30am by the new clock.
• Night owls may find the first few nights easier, because the change pushes the alarm later in their body's day. Dark mornings tend to become their challenge as winter goes on.
• Anyone already short on sleep may feel the week more, because there is less in reserve.

A day-by-day reset for your first week

You do not need a complicated plan. These steps work with your body clock rather than against it, and most of them follow NHS advice for sleeping well.

The first morning: get up at your usual time

Get up at your normal time by the new clock, even if you slept badly. A long lie-in feels kind, but it leaves you less sleepy at bedtime, so the next night and the next morning are harder. The NHS advises sticking to your regular sleeping hours rather than sleeping in after a bad night. A fixed wake-up time is the anchor for everything else in this plan.

Days one to three: use light on purpose

Research on how light resets the body clock shows a simple pattern: light in the morning tends to move the clock earlier, while light in the evening tends to move it later. After the clocks go back, your body clock needs to move about an hour later. So this week:

• Get daylight every day, and make the afternoon count. A walk before it gets dark, a late lunch outside or the school run on foot all help. Short spells outside still add up.
• Keep the lights bright until your wind-down hour. A well-lit kitchen and living room in the early evening helps your clock drift later, which is the direction you need.
• If you are waking too early, keep the first hour dim. Bright light straight after an early wake-up nudges the clock earlier still, so leave the big lights off and the curtains closed until your usual time.

Days one to seven: keep the rest of your day on the new clock

• Eat at normal clock times. Regular meals help anchor your day. Avoid a large meal late at night, which the NHS lists among the habits that get in the way of sleep.
• Move your caffeine cut-off earlier. The NHS suggests no tea, coffee or alcohol, and no smoking, for at least six hours before bed. In one sleep study, a large dose of caffeine taken six hours before bedtime still noticeably reduced sleep.
• Skip naps if you can. The NHS advises avoiding daytime naps if you are struggling to sleep. A nap uses up some of the sleepiness you need at night.
• Do not doze off on the sofa at 8pm. This is the classic clocks-back mistake. An early-evening doze takes the edge off your night-time sleepiness and makes an early wake-up more likely. If you feel heavy early in the evening, get up and do something light: tidy the kitchen, call a friend or take a short walk.
• Exercise earlier in the day. Regular exercise is good for sleep, but the NHS suggests avoiding it in the four hours before bed.

Every evening: a dim, calm last hour

Give yourself at least an hour to wind down before bed, as the NHS recommends. Dim the lights, put your phone and other screens away, and choose something calm, such as a bath, a book or gentle stretching. Keep the bedroom dark and quiet, using curtains, blinds or an eye mask if you need to. Then go to bed when you feel sleepy, not just because the clock says so, and get up at the same time each morning.

If you are waking too early

This is a common complaint after the autumn change, especially for natural early risers. On top of the steps above:

• Keep the bedroom properly dark in the early morning. Sunrise now comes an hour earlier by the clock, so blackout blinds or an eye mask can make a real difference this week.
• Try not to check your phone or the clock if you wake at 5am. The screen light and the mental arithmetic both make it harder to drift off again.
• If you are falling asleep too early, move your bedtime later by about 15 minutes every few nights until you wake at a time that suits you.

Darker evenings after the first week

Once your sleep has settled, the bigger challenge is the season itself. From now until spring it will be dark by teatime, and many of us spend most daylight hours indoors.

• Get daylight every day. The NHS advice for people who find winter hard is to get as much natural daylight as you can. A lunchtime walk is one of the easiest ways to do it.
• Keep your sleep and wake times steady, weekends included. Big swings at the weekend can feel like a mini clock change every Monday.
• Night owls: make use of the mornings. As mornings get darker, open the curtains as soon as you get up and get outside early when you can. Morning light helps stop your body clock drifting later through the winter.
• Keep moving and stay in touch with people. Both feature in the same NHS advice.

A note on mood. For some people, the switch to darker evenings comes with a dip in mood. A large Danish study of hospital records found an 11% rise in hospital contacts for depression after the autumn change, which faded over about ten weeks. That shows a link, not a cause, and most people are not affected this way. If low mood lasts, stops you enjoying things or worries you, speak to your GP. Seasonal affective disorder (SAD) is a recognised type of depression that tends to come back each winter, and help is available.

Vitamin D is the other autumn change. The NHS advises everyone to consider taking 10 micrograms of vitamin D a day from October to early March, because UK sunlight is not strong enough for your skin to make it then. Our winter guide to vitamin D3, K2 and magnesium covers amounts and timing in more detail.

Where magnesium fits at bedtime

No supplement can move your body clock for you. Light, a steady wake-up time and a calm evening do that job. But if you like to include a supplement in your evening wind-down, it helps to know exactly what you are taking and how it fits.

Vita London Bedtime Complex combines magnesium glycinate with KSM-66 ashwagandha root extract and smaller amounts of lemon balm, lavender, passion flower and chamomile extracts. A two-capsule serving contains 300mg of KSM-66 ashwagandha root extract and 100mg of magnesium glycinate.

Take it as directed: two capsules a day, preferably with a meal, so your evening meal is an easy anchor. Ashwagandha is not suitable for everyone. Avoid it if you are pregnant or breastfeeding, have a thyroid or autoimmune condition, or are due to have surgery, and ask a pharmacist or GP first if you have a liver condition or take any medicines.

If you would rather keep things simple, or ashwagandha is not right for you, Magnesium Glycinate capsules provide magnesium on its own, with no herbal extracts. A two-capsule serving contains 1000mg of magnesium glycinate, providing 180mg of magnesium. That is 48% of the nutrient reference value (NRV), the daily amount used as a guide in the UK. Magnesium contributes to normal psychological function and to the normal functioning of the nervous system. Our magnesium glycinate guide explains how to fit it into your day.

What to expect, and when to speak to your GP

By the end of the first week, most people find their sleep has settled into the new clock time. You will often notice it first in the mornings: the alarm wakes you, rather than your body beating it. It can take a little longer if you were already short on sleep or your days are irregular, so keep the steps above going for a second week if you need to.

Speak to your GP if changing your sleep habits has not helped, if you have had trouble sleeping for months, or if poor sleep is making daily life hard to cope with. And if you feel very sleepy during the day, do not drive until you have rested.

Quick questions

When do the clocks go forward again?

On Sunday 28 March 2027 at 1am, when British Summer Time begins. You lose an hour that night, and the spring change is usually the harder one to adjust to, so it is worth protecting your sleep in the week before.

Should I go to bed earlier because I feel sleepy earlier?

Not by much. Going to bed very early tends to lock in early waking. Aim for close to your usual bedtime by the new clock, go to bed when you feel sleepy, and keep your wake-up time fixed.

Can I prepare for the clock change next time?

Yes. A practical approach is to move your bedtime, wake-up time and meals by 10 to 15 minutes a day for a few days beforehand, in the direction of the change. Before the spring change that means a little earlier each day; before next October's change, a little later.