Is there a best time of day to build a habit?

Morning or evening habits: the one direct test

Very few studies have taken the same new habit, placed it at different times of day and measured how fast it became automatic. The one most often quoted is Fournier et al., 2017, published in the journal Health Psychology.

The team followed 48 students for 90 days as they took up a single health behaviour: a hip-flexor stretch (the psoas iliac stretch). Each student was randomly assigned to do it either right after waking up or just before going to bed. Every day a phone app asked how automatic the stretch felt, using a standard self-report scale, and every 30 days it prompted a saliva sample so the researchers could measure cortisol.

Automaticity climbed faster in the morning group. The researchers fitted a learning curve to each group and extended it to find the point where it levelled off: about day 106 for the morning stretchers and about day 154 for the evening ones.

Two things to keep in mind before you move everything to 7 a.m. Neither number was observed, because the study ended on day 90; both are projections from the curves. And the habit was one quick stretch. The lead author told TIME: “We asked participants to repeat an easy and quick behavior, which is not the same as a more complex behavior like exercising.” We could not find a published replication.

The cortisol idea, and why it is still a hypothesis

Cortisol follows a daily rhythm. It rises sharply over the first 30 to 45 minutes after waking, a pattern known as the cortisol awakening response (Stalder et al., 2016), and it is close to its lowest point at bedtime. Because cortisol had already been linked to habit learning, Fournier’s team asked whether doing something while cortisol is high helps it stick.

In their data, the cortisol level at the moment of stretching statistically mediated when the stretch became automatic. That fits the hypothesis, but a mediation analysis in 48 people only shows the numbers lining up the way the idea predicts. It can’t exclude other routes. The authors named some themselves: the stretch may have felt easier or more satisfying in the morning, or simply been easier to remember right after getting up.

The sample was also narrow on purpose. Participants were healthy, normal-weight non-smokers who were not using hormonal contraception, since weight, smoking and hormonal birth control all affect cortisol. Fournier told TIME that cortisol patterns differ from person to person and depend on stress, so the results may not apply to everyone. If you read online that morning habits work because of cortisol, treat it as a plausible idea with one small study behind it.

Why the same time every day matters more than which time

The stronger evidence is about consistency. In two diary studies by Wood, Quinn & Kashy, 2002, habits were defined as behaviours done almost daily in stable contexts. While doing them, people tended to think about something else, and they reported less stress than during non-habitual actions. Their review with Rünger (Wood & Rünger, 2016) sums up the field in one line: people tend to repeat the same behaviours in recurring contexts, and habits form as those responses get repeated in a given context.

Time of day is part of that context, and so is whatever usually happens around it. When the context breaks, habits break with it. Wood, Tam & Witt, 2005 followed students transferring to a new university: their exercise, newspaper and TV habits survived the move only when parts of the setting stayed the same.

Exercise data point the same way. Among 375 people in the US National Weight Control Registry (Schumacher et al., 2019), 68% did most of their workouts in the same time window. They exercised a little more often (4.8 vs 4.4 days a week) and were more likely to meet the 150-minutes-a-week guideline (86.3% vs 74.2%). Exercise levels did not differ by which window people chose. A one-year follow-up with 709 participants (Schumacher et al., 2021) found that consistent timing went with more automaticity over time, and the link was strongest for early-morning exercisers, who were also the most likely to keep the same slot a year later.

Those registry studies are observational and self-reported, and the people in them had already lost weight and kept it off. They can’t show that picking a fixed slot causes anything. Still, the pattern matches the lab work: a fixed slot gives the habit the same surroundings every day, and early mornings tend to stay fixed because fewer things compete for them.

Clock time or daily event: which cue to use

“Time of day” can mean two different cues. One is the clock: 7:15, or a phone alarm. The other is an event that happens at roughly that time anyway, like finishing breakfast, sitting down at your desk or turning off the TV. Habit researchers count both as context. A guide for doctors by Gardner, Lally & Wardle, 2012 suggests choosing “a time and place that you encounter every day” and gives as examples an event (“when I get to work”) or a time of day (“after breakfast”).

The two did not behave the same in a four-week study by Stawarz et al., 2015. Phone reminders helped people repeat the behaviour, but leaning on them held back habit development, while tying the behaviour to an event in the daily routine led to higher automaticity. The plausible reason is that a reminder does the remembering for you, so your brain never has to link the action to anything in your day.

The cues people chose in the best-known habit-formation study, Lally et al., 2010, included events tied to a point in the day, for example a 15-minute run before dinner, a piece of fruit with lunch, 50 sit-ups after morning coffee (BPS Research Digest). The time of day comes along for free. If you want the exact wording for this kind of plan, see if-then plans.

What if you are not a morning person?

People differ a lot in when their body wants to sleep and wake. Across more than 55,000 people who filled in the Munich ChronoType Questionnaire, sleep times formed a near-normal curve, with extreme early types getting up around when extreme late types go to sleep (Roenneberg et al., 2007). Chronotype also shifts with age and differs between men and women.

Nobody has tested whether late types build habits faster in the evening, so there is no evidence either way. What we do know points to a practical rule: choose the part of your day that is most predictable for you. For a night owl whose mornings are a rush, “after I wake up” is a moving target, while “after I close the laptop at night” may happen at the same point every day. A slot that keeps getting skipped won’t become automatic, whatever time it is.

How to pick the best time of day for each habit

Think of your day in three parts and look for events that happen in each one almost every day. Then match the habit to the part that suits it.

• Morning suits short habits you want every single day: a stretch, a glass of water, a few lines in a journal, taking a supplement. Mornings tend to have the fewest interruptions, and both the Fournier study and the exercise registry data lean slightly this way.
• Afternoon suits habits that break up the day: a walk after lunch, a water refill when you return to your desk, a short review of tomorrow’s tasks before you stop work. Lunch and the end of the working day are anchors most people hit reliably.
• Evening suits habits that close the day: reading, tidying the kitchen, laying out clothes, writing down one thing that went well. Brushing your teeth is close to the most reliable anchor there is.
• Habits that depend on other people or on energy, like a hard workout, go where you control the slot. If your evenings get taken by work or family, that is a reason to move the workout, not to give up on it.

1. Write down what happens every day at about the same point: waking up, coffee, commute, lunch, getting home, dinner, brushing teeth.
2. Attach each new habit to one of those events, in the part of the day where it fits.
3. Keep it there for a few weeks even when another time would be more convenient on a given day. Moving it around resets the cue.
4. Use a reminder as a backup while the link is new, and expect to need it less over time.
5. If you keep missing the slot, change the anchor, not the habit.

What the research does not tell you

• It does not prove that mornings are better. The only randomized comparison used one short stretch, 48 students and projected end points.
• It does not show that cortisol is the reason. That is the authors’ hypothesis, supported by a single mediation analysis.
• The consistency findings for exercise come from observational, self-reported data on people who had already kept weight off for years.
• Nobody has tested whether chronotype changes the best slot for building a habit.
• All of these studies measure automaticity by asking people how automatic a behaviour feels. That is the standard method, and it relies on self-report.

What holds up across the studies: a behaviour repeated in the same context, at the same point in the day, gets easier to start and needs less thought. How long that takes varies a lot from person to person; see how long it takes to form a habit. And if a busy day knocks your slot out once, that is not where habits fail; see what a missed day does.