Circadian-informed Optimal Bedtime

The goal of this interventional study is to test whether circadian-informed bedtime recommendations can improve sleep, next-day psychomotor vigilance, and subjective well-being among healthy adults. The main questions it aims to answer are: * Can Optimal Bedtime derived from data collected by a consumer smartwatch increase the objective total sleep time? * Can Optimal Bedtime derived from data collected by a consumer smartwatch reduce the count of lapse in a next-day Psychomotor Vigilance Task? * Can Optimal Bedtime derived from data collected by a consumer smartwatch increase subjective sleep quality? Researchers will compare Optimal Bedtime with a placebo bedtime and an unguided baseline in a cross-over design. Participants will: * Be randomized 1:1 to either Optimal Bedtime then placebo or placebo then Optimal Bedtime. * Wear a consumer smartwatch for 6 weeks, 2 weeks in each of baseline, Optimal Bedtime, and placebo. * Complete a Psychomotor Vigilance Task and a subjective well-being survey every morning.

Inclusion Criteria: * Adults aged 18 to 60 * English-speaking * Residence of the U.S. * Owner of a Samsung Galaxy Watch paired with an Android phone Exclusion Criteria: * Shift work schedule * Current smoker or currently using recreational drug * Diagnosis of any sleep or circadian rhythm disorder * Currently taking medications that may inhibit melatonin production * History of traumatic brain injury, stroke, or seizure * Plan of traveling across time zones during the study