Most people have a relatively consistent wake-up time. Fewer people have a set bedtime, which could be why you feel a lack of 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 focused all day, every day. Without consistent focus, your to-do list can pile up, leading you to frantically rush to get things done. And when we rush, we make mistakes. Now the time you intended to save is spent going back or catching up.
“The problem is that people get enough sleep over the course of a week, but it’s very messy,” says Vanderkam, who wrote eight pounds on time management. “One night you stay up too late and get up too early in the morning. The next night someone crashes on the couch…and weekends are everywhere.”
In spring 2021, Vanderkam surveyed more than 150 participants who spent nine weeks implementing nine predefined rules for productivity, especially by respecting a consistent bedtime. “One of the people in my study called [setting a bedtime] It’s the least sexy, but most impactful rule of all,” says Vanderkam.
A July 2025 study published in Nature, a peer-reviewed medical journal, came to a similar conclusion. Researchers observed more than 79,000 working adults in Japan and found that irregular bedtimes were linked to lower productivity and greater disengagement at work.
Bedtime “gives shape to the entire day,” Vanderkam says, adding that it helps you know how many hours you need to work each day, which helps you plan your time more effectively. “We know that the day has a beginning. People are a lot fuzzier about the idea that every day has an end, but it does. And everything you’re going to do has to fit into that time. It’s kind of a puzzle.”
Vanderkam established a 11 p.m. bedtime for herself years ago, and says the routine “allows me to make more rational choices about what’s actually going to fit into my day.”
Sleep disorders 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 the time your body naturally wakes up without an alarm for a few days and make 30-minute adjustments if necessary, 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,” Salas said. “I can’t think of one thing where sleep isn’t important.”
Most adults need about seven hours of sleep per night, according to Mayo Clinicbut sleep experts generally say that each person tends to need a different amount. Once you’ve determined how much sleep helps you feel mentally sharp each day, use that number to reverse engineer your ideal bedtime, advises Vanderkam.
“Look at what time you need to wake up, count how many hours you need to sleep, and we have bedtime,” says Vanderkam.
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