An extra hour, in theory.

At 2am on Sunday 25 October, the UK clocks change ending British Summer Time, and returning us to GMT. An extra hour in bed sounds like a gift. Your body clock, however, doesn’t read the clock on the wall. It reads light, and from this weekend there is much less of it at the end of the day. 

Do we really gain an hour?

For one night, largely yes. In a study of 11,780 UK Biobank participants, people slept about 33 minutes longer on the Sunday of the autumn change than on the Sundays either side of it. [2] After that the gain fades quickly: weeknight sleep was only around three minutes longer than the week before, which suggests the effect is short-lived. 

Earlier, smaller studies paint a less generous picture. A review of clock-change studies reported less sleep for about a week after the autumn change, because people kept waking early. [3] A small actigraphy study of 14 healthy students found earlier get-up times and less time in bed and total sleep after the autumn transition. [4] So the honest summary is that the extra hour is real on the night, modest after it, and individual. 

Why light is the real clock

The body’s internal clock is set mainly by light, and timing matters. Light in the evening can delay the biological clock, while morning light can shift it earlier. [5] The clocks going back is, in one sense, kind to the body: the American Academy of Sleep Medicine argues that standard time, which in the UK means GMT, aligns best with human circadian biology. [6] But earlier darkness means the evening signals arrive sooner, and we have to manage them deliberately. 

Five things worth doing from Monday

1. Keep your usual wake time. Treat Monday as a normal morning rather than the start of a lie-in, so the new clock time has something to anchor to. This is widely recommended general sleep advice rather than something the studies above test directly.

2. Get outside early. Morning light is the clearest signal that the day has begun. It is worth knowing the evidence is not one-sided: in a field study, increasing morning light through curtains advanced neither melatonin nor sleep timing, whereas reducing evening blue light advanced both. [7] Morning light is a good habit, but the evening may matter as much. 

3. Lower the lights after dark. Compared with dim light, exposure to ordinary room light before bedtime suppressed melatonin and shortened its duration by about 90 minutes. [8] Switch the overheads for lamps, use warm bulbs, and move screens out of the last hour where you can. 

4. Bank daylight across the day. Greater daytime light exposure may reduce how strongly evening light shifts the body clock. [9] A lunchtime walk now does more work than it did in July. 

5. Keep the bedroom cool, not cold. The winter risk is overheating rather than chill. In real-life conditions with bedding and clothing, heat exposure increases wakefulness and reduces slow-wave and REM sleep, while cold exposure did not affect sleep stages. [10] Turn the heating down overnight and use layers rather than a warm room. 

A winter evening ritual

None of this replaces the basics, and if sleep difficulty lasts for weeks, speak to your GP. For the ordinary, adjusting-to-winter nights, a consistent evening ritual helps you hold the routine through the darker months.

That is the thinking behind Was It All A Dream?, our evening formula. It combines valerian root, Montmorency cherry and passionflower in a liquid with peppermint and sweet fennel, to be taken as part of a calm evening routine alongside the habits above. 

Discover Was it All a Dream?

References

1. UK clock change date, 2am Sunday 25 October 2026: GOV.UK (gov.uk/when-do-the-clocks-change) and press coverage, e.g. Express & Star, “UK clocks will go back in October 2026”.
2. de Lange M, et al. The effects of daylight saving time clock changes on accelerometer-measured sleep duration in the UK Biobank. J Sleep Res. 2025 (confirm volume and page details)
3. Harrison Y. The impact of daylight saving time on sleep and related behaviours. Sleep Med Rev. 2013 (confirm details)
4. Tonetti L, Erbacci A, Fabbri M, Martoni M, Natale V. Effects of transitions into and out of daylight saving time on the quality of the sleep/wake cycle: an actigraphic study in healthy university students. Chronobiol Int. 2013
5. Early evening light mitigates sleep compromising physiological and alerting responses to subsequent late evening light. Sci Rep. 2019;9:16064 (add authors)
6. American Academy of Sleep Medicine. Permanent standard time is the optimal choice for health and safety: a position statement. J Clin Sleep Med. 2024;20(1):121-125. doi:10.5664/jcsm.10898
7. Strategies to decrease social jetlag: reducing evening blue light advances sleep and melatonin (add authors and journal details)
8. Gooley JJ, Chamberlain K, Smith KA, et al. Exposure to room light before bedtime suppresses melatonin onset and shortens melatonin duration in humans. J Clin Endocrinol Metab. 2011
9. Daytime light exposure and circadian phase shifts to bright evening or morning light. Sleep Med. 2011;12(8):805-807. doi:10.1016/j.sleep.2011.02.005 (add title and authors)
10. Okamoto-Mizuno K, Mizuno K. Effects of thermal environment on sleep and circadian rhythm. J Physiol Anthropol. 2012;31:14. doi:10.1186/1880-6805-31-14
11. National Center for Complementary and Integrative Health (NIH). Valerian. nccih.nih.gov/health/valerian
12. Mayo Clinic. Valerian: a safe and effective herbal sleep aid? mayoclinic.org