Most people have a relatively consistent wakeup time. Fewer have a set bedtime, which could be the reason you feel lacking in free time during the day, says author and time management expert Laura Vanderkam.
The logic works like this: Without consistent sleep habits, most people can be generally productive but struggle to stay consistently focused all day, every day. Without consistent focus, your task list can build up, leading you to frantically rush to get things done. And when you’re rushing, you make mistakes. Now the time you intended on saving is being spent backtracking or playing catch up.
“The problem is that people will get enough sleep over the course of a week overall, but it’s very disordered,” says Vanderkam, who’s written eight books about time management. “One night, you’re staying up too late and getting up too early in the morning. The next night, somebody’s crashing on the couch … and weekends are all over the map.”
In spring 2021, Vanderkam surveyed over 150 participants who spent nine weeks implementing nine preset rules for productivity, including sticking to a consistent bedtime. “One of the people in my study called [setting a bedtime] the least sexy, but the most impactful rule of all of them,” says Vanderkam.
A July 2025 study published to Nature, a peer-reviewed medical journal, came to a similar conclusion. Researchers observed over 79,000 working adults in Japan and found that irregular bedtimes were linked to lower productivity and more disengagement at work.
A bedtime “gives shape to the entire day,” Vanderkam says, adding that it helps you know how many hours you have to work with each day, which helps you schedule your time more effectively. “We know the day has a beginning — people are a lot fuzzier on this notion that each day has an end, but it does. And everything you’re going to do has to fit within that time. It’s kind of a puzzle.”
Vanderkam set an 11 p.m. bedtime for herself years ago, and says the routine “allows me to make more rational choices about what is actually going to fit in my day.”
Disordered sleep can also negatively impact your circadian rhythm, or your body’s innate sleep-wake pattern, Rachel Salas, a sleep neurologist and professor at Johns Hopkins University, told CNBC Make It in July 2022. To find yours, observe what time your body naturally wakes up without an alarm for a few days, and make 30-minute adjustments if you need to, Salas recommended.
“Sleep is a basic human need, and a lot is at stake if we don’t get enough of it: our cognition, our memory, our digestion,” said Salas. “I can’t think of one thing sleep isn’t important for.”
Most adults need around seven hours of sleep per night, according to the Mayo Clinic, but sleep experts typically say that each person tends to need a different amount. Once you determine how much sleep helps you feel mentally sharp each day, use that figure to reverse-engineer your ideal bedtime, Vanderkam advises.
“Look at what time you have to wake up, count back the number of hours that you need to sleep, and we have a bedtime,” says Vanderkam.
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