Clocks Go Back: What the Time Change Does to Your Body Clock

In the UK and most of Europe the clocks go back on Sunday 25 October 2026, in the US and Canada on Sunday 1 November. Your phone has the new time at once; your body takes a while. Here is what happens that night, who feels the autumn change more and how to prepare in four small steps.

What happens that night

When the clocks go back, one hour of the night happens twice: in the UK, 2:00 am BST becomes 1:00 am GMT; in central Europe, 3:00 am becomes 2:00 am; in the US and Canada, 2:00 am becomes 1:00 am. That Sunday has 25 hours. If you go to bed at 11 pm and get up at 7 am as usual, you spend nine hours in bed instead of eight that night.

After that, the clock runs an hour behind your body: when it shows 7 am, your body still thinks it is 8 am summer time. Your alarm feels later, but in the evening you get tired an hour earlier by the clock. Hunger and the afternoon slump also arrive an hour earlier than the clock suggests at first.

Why your body doesn’t just jump

Your body clock sets itself by light, not by the time on the clock. In 2007, Kantermann and colleagues analysed a survey of 55,000 people: under standard time, their sleep times on free days followed sunrise through the year; under daylight saving time, they did not. [1]

How quickly people adjust varies. In a second study by the same group with 50 people, sleep and activity adjusted quickly to the autumn change but not to the spring change, especially in late chronotypes. [1] In a small Finnish study with nine participants wearing wrist activity monitors, sleep and activity were still not fully adjusted four days after the change. [2]

Who feels the autumn change more

In the Finnish study, the autumn change disturbed morning types more, the spring change evening types. [2]

If you wake up early anyway, you wake up even earlier by the clock after the change, say at 5 instead of 6, and lie awake. Evening types get an hour back: their alarm rings an hour later for their body. The chronotype calculator shows which type you are.

Your plan for the clock change

If the change is hard on you, you can prepare in small steps: from Wednesday, move bedtime and wake-up time 15 minutes later each day. By Sunday, clock and body match again. If you cannot get up later during the week, two steps of 30 minutes on Friday and Saturday are enough.

Light helps

Light in the evening moves your body clock later; bright light right after waking early in the morning moves it earlier. [3] In autumn you want it later. So bright light in the evening helps, and so does a dim start if you wake very early in the first days.

What Circadian does that night

In Circadian’s sleep review, every night sits on an axis of clock times. On the night the clocks go back, one hour happens twice. If you sleep from 1:50 am BST to 1:10 am GMT, for example, that is 20 minutes of sleep even though the clock runs backwards. Circadian splits such a stretch into two parts so that both clock times are right. In spring, when an hour is skipped, the app records no sleep in it. The app’s own tests cover both cases.

In the days after the change, the review shows how your sleep and wake-up times shift and whether they return to your usual sleep time.

What if the clocks stopped changing?

The European Commission proposed ending the clock changes in 2018. [5] This has not been implemented. In the US, the American Academy of Sleep Medicine (AASM) supports permanent standard time, today’s winter time, because it aligns best with human circadian biology. [4]

This article is for general information only and does not replace medical advice. Consult your doctor for health-related questions.