The best time to sleep and wake up: lessons from Russell Foster

Here is an example of the best time to sleep: if you have to get up at 6:30 a.m., aim to be asleep by 11:30 p.m. at the latest, which leaves room for the seven or more hours recommended for adults. Your numbers will differ, because no clock time suits everyone. The best time is a window your own body clock can keep every night, so pick a wake time you can hold seven days a week, count back from it, and use light to pull your clock towards it.

Russell Foster, Professor of Circadian Neuroscience at Oxford, has spent his career on why people's clocks differ. Around 1991 he proposed that the eye holds a third kind of light sensor whose job is to set the body clock; at one talk a heckler shouted a one-word verdict we can't print, and it took about a decade to win the argument. Ask him for the biggest myth about the body clock and he names the idea "that we are all the same."

"Good sleep" is like shoe size, "one size does not fit all." (Russell Foster, Becoming Sleep Wise)

Choose times you can keep every day

Once you know roughly where your clock sits, consistency seems to matter more than the exact hour. In a study of 60,977 UK Biobank participants who wore wrist trackers for a week and were followed for about six years, those with more regular sleep had a 20 to 48% lower risk of dying from any cause than the least regular fifth, after adjusting for health and lifestyle. Regularity predicted that risk better than sleep length did, and the link held after allowing for whether people slept early or late. The study shows a link and can't prove cause, but the authors note regularity "may also be an easier dimension to target." Our guide to a fixed wake time goes deeper.

Choose your wake time first

Rebecca Robbins, a sleep scientist at Brigham and Women's Hospital and Harvard Medical School, starts with the calendar: find the earliest time you have to be up in a typical week, and set that alarm for all seven days.

Count back far enough

The American Academy of Sleep Medicine and the Sleep Research Society recommend that adults aged 18 to 60 sleep 7 or more hours a night on a regular basis. Robbins counts back nine hours to set the time you start getting ready for bed, which covers winding down and people who need more. With a 6:30 a.m. alarm, that puts the start of your wind-down at 9:30 p.m. What you do in that wind-down is covered in our guide to how to sleep better.

Is it bad to sleep in on weekends?

Robbins recommends sleeping in no more than an hour. Experts agree on a limit like that but differ on the reason. For Foster, a lie-in of two or three hours means you're not getting enough sleep during the week: you partly catch up, still start Monday with a sleep debt, and miss the morning light that sets your clock. A 2019 review by Till Roenneberg's team in Munich is kinder to the lie-in. It calls it a common misconception that the harm comes from sleeping in, and cites a large cohort study in which short weekday sleepers who got no weekend catch-up sleep had higher mortality than those who did.

Either way, if you need a long lie-in, move your weeknight lights-out earlier. Keep the lie-in short anyway, because the clock follows your sleep fast: the review cites studies in which the body's timing markers shifted about 45 minutes after two days of moved sleep times. The 1h Protocol for Better Sleep takes a middle path on free days: get up at your usual time, get your light, then go back to bed for an hour if you want it.

Find your own best time to sleep

Where your body clock sits is your chronotype. Foster estimates that most people, about 65%, are "doves" between the early larks and the late owls. Roenneberg's review traces the differences to genes, light and age, and the light part is why your timing can move.

Ask yourself the desert-island question

Matthew Walker, the UC Berkeley sleep scientist, asks people one question: if you were on a desert island with no responsibilities, what time would you go to bed, and when would you wake? He has met people convinced they had a sleep problem who may simply have had a clock that ran later than their job allowed. Night owls, he says, have long been called lazy for something that is genetic, and "when you fight biology you normally lose."

Researchers use the same idea with real data: the midpoint of your sleep on free days, with no alarm set. Fall asleep at 1 a.m. and wake at 9 a.m., and your midpoint is 5 a.m. Count from when you fell asleep, not when you got into bed. If you're catching up on lost sleep, the midpoint looks later than your clock really is, so the Munich questionnaire corrects for oversleep.

Check that you're getting enough

Foster's test is practical. You're probably short of sleep if you need an alarm to get out of bed, oversleep on free days, take a long time to wake up, feel sleepy and irritable in the day, crave a nap or need caffeine to keep going. Our guide to sleep deprivation covers what falling short does. If you keep regular times with seven or more hours for sleep and still feel very sleepy by day, talk to a doctor.

Expect it to change with age

In the Munich data, chronotype gets later from about age 10 to around 20, then earlier for the rest of life. Walker describes 15-year-olds who can't fall asleep at 9 p.m. because their clocks have moved later: "It's biology." Foster, a very late chronotype himself, says early starts have become easier with age.

Work out your social jet lag

The sleep diaries Roenneberg's team studied often looked as if people flew several time zones west every Friday evening and back on Monday morning, without leaving home. They called it social jet lag. To measure yours:

• Find your sleep midpoint on workdays. Asleep from 11:30 p.m. to 6:30 a.m. gives 3 a.m.
• Find it on free days. Asleep from 1 a.m. to 9 a.m. gives 5 a.m.
• The difference, two hours here, is your social jet lag.

It's usually biggest in late chronotypes and in teenagers facing early school starts.

How to fix your sleep schedule with light

About 90% of people, Foster explains, have a body clock that runs slightly longer than 24 hours, so without a daily nudge it slides later. Morning light moves the clock earlier; evening light moves it later. In one of his studies, the later a student's chronotype, the more evening light they got and the less morning light, which pushed their clocks later still.

Get outdoor light within an hour of waking

Foster has measured it with a light meter:

So go outside if you can. A light researcher at the US National Institute of Mental Health suggests getting out even if you stay in the shade, and staying out longer when it's cloudy, since even a cloudy day is far brighter than a room.

Dim your evenings from three hours before bed

A 2022 consensus of light researchers recommends very low light at eye level (no more than 10 melanopic lux, a unit weighted for the clock's light sensors) from at least three hours before bedtime, and a bedroom as dark as possible. At home, that means desk lamps or lights placed low instead of overhead lights.

Foster worries less about screens than you might expect. He puts an e-reader at full brightness at about 30 lux, and cites studies in which plenty of bright light during the day canceled out even subtle effects of dim evening light. A bright day protects your evening.

Give it weeks, and keep going

After a long flight, Foster says, it can take a day for every time zone crossed for the clock to catch up. Moving your alarm two hours earlier overnight is like flying two time zones east.

In one study cited in Roenneberg's review, late types who followed three weeks of instructions for stronger, more regular light and dark moved their sleep and other clock markers about two hours earlier. The same review warns that chronotype has a genetic basis, and people drift back once they stop. The 1h Protocol for Better Sleep takes the slow route for late clocks: a fixed wake time, morning light, dim evenings, and lights-out about 20 minutes earlier every three nights until sleepiness arrives on time.

Check your week

Each weekend, count the days you kept your wake time and got morning light, and work out your social jet lag again. If the gap is shrinking, your clock is moving your way. Foster's own test is shorter: "If you can operate at a high level during the day, you are fine."

This article draws on Russell Foster's interviews with ZOE and Feel Better, Live More and his essay for Yale University Press, with research and advice from other sleep and light scientists. Full list below.

The full 1h Protocol for Better Sleep works out your own times from your answers: your wake time, when to get light, when to dim the house and how fast lights-out moves. Find your times: start the free part, which finds your sleep pattern and gives you a first step for tonight.

Frequently asked questions

What is the best time to go to sleep?

No single time suits everyone. The best time to sleep gives you at least seven hours asleep before a wake time you can keep every day, and fits your chronotype. If you get up at 6:30 a.m., for example, be asleep by 11:30 p.m. at the latest.

How do I fix my sleep schedule fast?

Your alarm can change overnight, but your body clock follows in steps, needing about a day per time zone after travel. The fastest levers are a fixed wake time, outdoor light within an hour of waking, dim evenings and no long lie-ins. In one study, late types who followed a similar light routine for three weeks moved about two hours earlier.

Is it bad to sleep in on weekends?

Most sleep experts suggest sleeping in no more than about an hour. Needing two or three hours means you're short of sleep during the week, and long lie-ins can push your clock later, so Monday feels like jet lag. The fix is an earlier weeknight bedtime.

Can a night owl become a morning person?

Partly. Late types have moved about two hours earlier after three weeks of stronger morning light and darker evenings, but genes set the starting point and their timing drifts back if they stop. Most people also get earlier with age after about 20.

How do I wake up early without feeling tired?

Get at least seven hours of sleep, keep the same wake time at weekends, and get outdoor light soon after waking. Move earlier gradually, because the body clock adjusts in steps.

Sources

• ZOE Science & Nutrition: How to make your body clock work for you, with Russell Foster (podcast episode, 2023, official transcript)
• Feel Better, Live More #424 with Russell Foster (podcast episode, 2024)
• Russell Foster, Becoming Sleep Wise (author essay, Yale University Press, 2023)
• Russell Foster, Life Time (publisher page and author biography, Penguin, 2022)
• Roenneberg et al., Chronotype and social jetlag: a (self-) critical review (review, Biology, 2019)
• Windred et al., Sleep regularity is a stronger predictor of mortality risk than sleep duration (prospective cohort study, Sleep, 2024)
• Watson et al., Recommended amount of sleep for a healthy adult (AASM and SRS consensus statement, 2015)
• Brown et al., Recommendations for daytime, evening and nighttime indoor light exposure (expert consensus, PLOS Biology, 2022)
• The Peter Attia Drive #126 with Matthew Walker (podcast episode)
• Huberman Lab with Samer Hattar: Timing light, food and exercise for better sleep (podcast episode, 2021, official transcript)
• Huberman Lab: Sleep Toolkit (podcast episode, 2022, official transcript)
• The Mel Robbins Podcast with Rebecca Robbins: How to stop waking up tired (podcast episode, 2024)

Education, not medical advice.