Most people have a relatively consistent wake-up time. Laura Vanderkam, author and time management expert, says that most people don’t set a specific bedtime, which may be the reason they feel like they don’t have enough free time during the day.
The logic goes like this: Without consistent sleep habits, most people are more productive but have a harder time staying focused all day, every day. Without consistent focus, your to-do list will grow and you’ll be scrambling to get things done. And when you rush, you make mistakes. The time you intended to save ends up being spent going back and catching up.
“The problem is that people should be able to get enough sleep throughout the week, but their sleep is highly disrupted,” says Vanderkam, who has written eight books on time management. “One night I stayed up too late and woke up too early. The next night someone crashed on the couch…and the whole weekend was a mess.”
In spring 2021, Vanderkam spent nine weeks implementing nine preset rules for productivity, such as sticking to a consistent bedtime, with more than 150 participants. “One of the participants in my study said[setting bedtimes]was the least sexy rule, but the most impactful,” Vanderkam says.
A July 2025 study published in the peer-reviewed medical journal Nature came to a similar conclusion. Researchers observed more than 79,000 working adults in Japan and found that irregular bedtimes were associated with lower productivity and difficulty concentrating on work.
Bedtime “shapes your entire day,” Vanderkam said, adding that bedtime can help you know how many hours you have to work each day, which can help you plan your time more effectively. “We know that each day has a beginning. People are much more vague about the concept that each day has an end, but it actually does have an end. And everything you’re trying to do has to fit within that time. It’s kind of a puzzle.”
Vanderkam set a bedtime for herself at 11 p.m. years ago, and says this routine has “allowed me to make more rational choices about what actually fits into my day.”
Rachel Salas, a sleep neurologist and professor at Johns Hopkins University, told CNBC Make It in July 2022 that disrupted sleep can also negatively impact circadian rhythms, or your body’s natural sleep-wake patterns. To find your sleep time, Salas recommended observing your body’s natural wake-up time for a few days without an alarm, then adjusting by 30 minutes as needed.
“Sleep is a basic human need, and when you don’t get enough sleep, many things are at risk, including cognition, memory, and digestion,” Salas says. “I can’t think of a single thing where sleep isn’t important.”
According to the Mayo Clinic, most adults need about seven hours of sleep a night, but sleep experts say the amount of sleep each person typically needs tends to vary. Once you determine how much sleep each day makes you feel mentally alert, Vanderkam suggests using that number to reverse engineer your ideal bedtime.
“You can determine your bedtime by looking at what time you have to wake up and working backwards to determine how much sleep you need,” says Vanderkam.
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