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The Clocks Went Back. Did You Get the Extra Hour of Sleep?
On Sunday morning most of Europe woke up to a small gift. The clocks had gone back, the phone had quietly agreed, and the radio announced the one piece of good news everyone repeats each October: an extra hour in bed. Next Sunday, 1 November, it is North America’s turn.
I like the ritual. I just don’t believe the gift. When researchers have actually measured what people do with that hour, most of it goes missing — and the more interesting story is not the night of the change at all, but the week after it.
The hour you were promised
The best evidence comes from wrists, not opinions. A team at the University of Bristol looked at 11,780 UK Biobank volunteers, aged 43 to 78, who happened to be wearing a research-grade accelerometer for a week that included a clock change. Their study, published in the Journal of Sleep Research, compared sleep on the Sunday of the change with the Sundays on either side.
In autumn, people slept about 33 minutes longer than the Sunday before, and 38 minutes longer than the Sunday after. Not 60. In the authors’ own phrasing, people did not, or could not, take advantage of the full extra hour.
Spring told the opposite story. On the morning the clocks went forward, people slept about 65 minutes less than the Sunday before. The lost hour is collected in full, with interest. The gained hour is paid out at roughly half.
That asymmetry is the whole joke of the clock change. The body is a reluctant creditor and a punctual debtor.
What the wrist recorded
Sleep on clock-change Sunday, compared with the Sundays either side
The week after the autumn change, in adults 45 to 85
Share reporting each problem, one week before vs one week after
Trouble falling asleep
Trouble staying asleep
Sleepy despite enough sleep
Three ways to read the clock change
The optimist: autumn is the kind change. The body clock follows it readily, and the extra sleep on the night itself is real, if only half an hour.
The sceptic: the hour is mostly spent waking early, and for a week some people sleep worse than before. A gift that keeps you up at 5 a.m. is a strange gift.
The useful middle: the change itself is small. What matters is what you do with the next ten mornings — when you get up, and how much daylight you see.
Top: de Lange et al., J Sleep Res 2025 (UK Biobank, n = 11,780, wrist accelerometer); dots are mean differences with 95% intervals, on a shared minutes scale. Bottom: Zolfaghari et al., Neurology 2023 (Canadian Longitudinal Study on Aging, n = 30,097); different people interviewed before and after; bar widths are the published percentages on a shared 0–13% scale.
Where the hour actually goes
The simplest explanation is the one every parent and dog owner already knows. Bodies do not read clocks. If you normally wake at 7, on Sunday your body still wakes at what it thinks is 7 — which the clock now calls 6. You lie there, you get up, the hour evaporates into an early coffee.
A 2013 review in Sleep Medicine Reviews by Yvonne Harrison put it plainly: the autumn change is popularised as a gain of an hour’s sleep, but there is little evidence of extra sleep on that night. Across the working week that follows, rise times run earlier for several days in a row, which the review reads as a net loss of sleep across the week, not a gain.
The Bristol data add a twist. On the weekdays after the autumn change, younger and employed people slept slightly more than the week before. The oldest third, aged 68 to 78, and retired people slept less. The people with no alarm clock to obey were the ones who ended up with less sleep.
The kind change is still a change
Everyone casts spring as the villain and autumn as the gift. The best-measured symptoms point the other way.
A Canadian study of 30,097 adults aged 45 to 85, published in Neurology in 2023, compared people interviewed in the week before a clock change with others interviewed in the week after. After the switch to standard time in autumn, the share reporting trouble falling asleep roughly doubled, from 3.3% to 7.1%. Trouble staying asleep rose from 8.2% to 12.9%, and sleepiness despite enough sleep from 3.6% to 7.3%. After the spring change, the authors found no such difference in symptoms, only a nine-minute shorter night.
Two caveats keep this honest. These were different people before and after, not the same people followed through the change, and the study only covered middle-aged and older adults. And the senior author told the press release the disruptions were brief: no longer evident two weeks after the shift. This is a fortnight of turbulence, not a lasting harm. But it is turbulence the folklore never mentions.
Your body clock prefers autumn anyway
Here is the part that rescues autumn’s reputation, on a different axis. In a 2007 study in Current Biology, Till Roenneberg’s group surveyed about 55,000 people in Central Europe and tracked 50 more for eight weeks around each transition. On free days, sleep timing tracked the season’s changing dawn under standard time, but not under daylight saving time. Sleep and activity readily adjusted when daylight saving ended in autumn. In spring, activity timing did not adjust, especially in late chronotypes — the night owls.
So the autumn change is the one your internal clock accepts, because it moves social time back towards sun time. The mornings are brighter, and morning light is the main signal that sets the body clock. The evenings are darker, which helps too. What you lose is not alignment. It is a week of slightly ragged sleep while the alarm clock and the body clock renegotiate.
The policy fight, and its softer numbers
Every October the clock change also restarts an old argument about scrapping it. Sleep scientists are unusually united here: the American Academy of Sleep Medicine’s 2020 position statement calls for abolishing seasonal changes in favour of fixed, year-round standard time, on the grounds that it fits human circadian biology best. Plenty of people would rather keep the light evenings. Reasonable people can disagree about the trade.
The most-quoted recent number in that debate comes from a 2025 Stanford modelling study in PNAS, which simulated light exposure under each policy and linked the resulting circadian burden to county health data. It is worth knowing what kind of evidence that is. It is a model, built on an idealised day of sleeping 10 to 7 and working indoors 9 to 5, and the authors call their estimates predictive rather than causal. The paper has since received a published correction for a coding error that let light appear after sunset, and two critical letters. The senior author himself said people’s real light habits are probably much worse than the model assumes.
None of that makes the direction wrong. It makes the precision wrong. When a headline converts a modelled fraction of a percentage point into hundreds of thousands of people, enjoy the argument and hold the number loosely.
What to do with the next ten mornings
You cannot vote on the clock this week. You can manage the fortnight it hands you.
- Keep your wake time on the new clock. If you wake early, get up at your usual new-clock time anyway rather than lying there negotiating. A fixed wake time does more for your sleep than any single long night — see our piece on sleep regularity versus duration.
- Spend the bright mornings outside. Mornings are briefly lighter after the change. Daylight soon after waking is the strongest cue the body clock has, and even an overcast morning outdoors is far brighter than a lit room. Our guide to light exposure and circadian health explains why.
- Don’t mistake 5 a.m. for insomnia. If you are older, retired or an early riser, waking an hour early this week is the clock change, not a new sleep problem. The Canadian data suggest it fades within about two weeks.
- Read the fortnight, not the night. A wearable such as the Agen Band estimates sleep from movement and heart rate. One night after a clock change tells you little. Two weeks of bedtime and wake-time trends tell you whether you have settled.
If poor sleep lasts well beyond a couple of weeks, or daytime sleepiness affects driving or work, talk to your doctor. That is not the clock change any more.
The bottom line
The extra hour is mostly a story. Wrist data show people gain about half of it on the night, and over the following week some — especially older adults without an alarm clock — sleep worse, not better, for a while. Yet autumn is still the change your body clock accepts most readily, because it pulls the clock back towards the sun. Think of the fortnight as a small recalibration: hold your wake time, find the morning light, and judge your sleep by its trend. The clock moved in one night. You are allowed two weeks.
