The Power of When

Learn the best time to do everything—from drink your coffee to have sex or go for a run—according to your body’s chronotype.

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Optimize Your Life

Do you know the best time for you to have sex, ask your boss for a raise, and  talk to your children? Exciting new research proves there is a right time to do just about everything, based on our biology and hormones. Dr. Breus’s The Power of When presents a groundbreaking new program for getting back in sync with your natural rhythm by making minor changes to your daily routine.

Take the Quiz and Learn Your Chronotype


Michael Breus, PhD

Michael J. Breus, PhD, is a clinical psychologist and both a diplomate of the American Board of Sleep Medicine and a fellow of the American Academy of Sleep Medicine. He was one of the youngest people to have passed the board at age 31 and, with a specialty in sleep disorders, is one of only 163 psychologists in the world with his credentials and distinction.

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  • “I haven’t come across this way of thinking, it is much more accurate than early bird/night owl. It takes into account a lot of good stuff, and I think this book is actually worth your time. If you’re into biohacking, you really, really want to read this book.

    Dave Asprey

    Author of The Bulletproof Diet

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  • Dr. Breus has succeeded in making the complex science of chronobiology accessible and engaging for all readers. Whether you’re looking to improve your relationships, get a raise at work, or simply lead a more fulfilling life, The Power of When is the guidebook you’ve been waiting for.

    Mark Hyman, MD

    Director, Cleveland Clinic Center for Functional Medicine

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  • The Power of When prepares you to take full advantage of our adaptation to the rhythms of nature. After reading this book, your decision-making ability will forever be improved. This is a new horizon in our understanding of human behavior, and Michael Breus masterfully presents the science as a recipe for self-improvement.

    David Perlmutter, MD

    Author of Grain Brain and Brain Maker

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What's Your Chronotype?

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