How to reset your circadian rhythm

What is your circadian rhythm?

Your circadian rhythm is your internal clock. It runs on a cycle of roughly a day and tells your body when to feel alert and when to wind down. Light is one of its main time cues: light in the morning is linked to an earlier clock, bright light late in the evening to a later one.

Modern life mixes these signals up. We spend most of the day indoors in dim light and then sit in bright screens and lamps at night. Research found exactly this pattern: people living with electric light got less sunlight during the day, more light after sunset and had a later body clock than under natural light only (Wright et al., 2013).

The three levers

Almost every useful tip comes down to three things. You do not need all of them perfectly; doing each of them most days is what counts.

• Morning light: go outside soon after you get up. As a rule of thumb, about 10 minutes on a clear morning, 15 when it is partly cloudy and 20 to 25 when it is overcast, up to 30 with a low sun.
• Dimmer evenings: from at least 3 hours before bed, use warmer, lower lamps and turn screen brightness down (Brown et al., 2022).
• A steady wake-up time: the time you get up anchors the whole day. Keep it within about an hour on weekends too.

How many minutes today? The morning light calculator estimates it for your weather.

Can you reset your circadian rhythm in one day?

Your body clock moves gradually. A big jump, such as getting up three hours earlier overnight, tends to leave you tired for days. Small steps of about 15 to 30 minutes, repeated with morning light each day, are easier to keep up and easier on your energy.

Give it several days rather than expecting a change overnight. In the camping study, the people who were later types moved the most once they lived with natural light only (Wright et al., 2013).

How long does it take to reset your circadian rhythm?

The 7-day plan below moves your wake-up time by one hour over a week. How quickly the new time feels normal differs from person to person. Small steps of 15 to 30 minutes with daily morning light are easier to keep than one big jump.

Does the time of day change how light resets your body clock?

Yes, and it can even reverse the direction. In a lab study with 21 healthy people, each person got one bright light session of 6.7 hours at about 10,000 lux, timed to a different point of their internal clock. Light given before the low point of core body temperature moved the clock later, light given after it moved the clock earlier, and light right at that point did not shift it (Khalsa et al., 2003).

That session was far longer and brighter than a morning walk. The study shows why timing matters, not how many minutes of everyday light you need.

Evening light counts even when it is not very bright. In another lab study with 23 young adults, one 6.5-hour light session early in the biological night delayed the clock. Dim room light of about 100 lux produced half the delay that bright light of about 9,000 lux did (Zeitzer et al., 2000). That is why the plan below dims the lamps in the evening.

What if you can’t get outside in the morning?

Some mornings do not work: it is still dark, you start early or the weather is rough. Take your daylight as early as you can later on, for example in a first break. Sitting by a window helps a little, but a few minutes outside usually get you far more light. On dark winter mornings, bright light indoors can make the wait easier.

Resetting your body clock: same plan, same levers

“Body clock” is the everyday word for your circadian rhythm, so resetting your body clock works the same way: a steady wake-up time, daylight soon after waking and dimmer evenings. The 7-day plan below covers both.

Does caffeine affect your circadian rhythm?

It can. In a lab study, caffeine equal to a double espresso, taken three hours before bedtime, shifted the internal clock about 40 minutes later. That was roughly half the shift caused by three hours of bright evening light (Burke et al., 2015). If you want to start your day earlier, keep your coffee to the morning.

When should you exercise to reset your body clock?

Timing matters. In a study with younger and older adults, one hour of moderate exercise at 7 am or between 1 and 4 pm moved the internal clock earlier, while exercise between 7 and 10 pm moved it later (Youngstedt et al., 2019). A morning walk outside gives you your daylight and early exercise at the same time; whether an easy walk shifts the clock the same way was not part of the study.

Do meal times reset your circadian rhythm?

Less than often claimed. In a small study with ten young men, moving all meals five hours later did not shift the main clock in the brain, but it delayed the body’s blood sugar rhythm by more than five hours (Wehrens et al., 2017). Regular meal times give your day structure; light stays the main time cue.

Why do teenagers find early mornings so hard?

On average, teenagers and young adults are later types than older adults (Fischer et al., 2017). That is normal, not laziness. The same levers apply: a steady wake-up time, morning daylight and small steps.

Early bird or night owl? Take the 2-minute chronotype quiz.

Weekends and “social jetlag”

Many people, especially later types, sleep much later on free days than on workdays. Researchers call this gap between social and biological time “social jetlag” (Wittmann et al., 2006). Keeping your weekend wake-up time within about an hour of your weekday time keeps the gap small.

Can you fix your sleep schedule in one day? An honest answer.

Shift work and long-haul travel

This plan is made for a regular day. With night shifts or long-haul flights, the timing of light needs its own planning; the expert recommendations name shift workers as a special case (Brown et al., 2022). Ask an occupational or travel medicine doctor for a plan that fits your schedule.

Long-haul flight ahead? How to time daylight for jet lag.

What research says

An international expert panel has published recommendations for how much light people should get during the day, in the evening and at night, together with a standard way to measure it (Brown et al., 2022).

After living with natural light only, participants’ internal clocks lined up with sunrise and sunset, and later types shifted the most (Wright et al., 2013).

The plan and the minutes on this page are a practical routine built on these ideas, not a medical program. If you have long-lasting trouble sleeping or staying awake, talk to a doctor.

A 7-day plan