A simple rule of thumb is to expose yourself to “bright days, dark nights.”

Daytime light exposure is crucial for resetting your clock. Seek out natural daylight or white light rich in short wavelengths during the day (e.g., outdoor lunch breaks, morning bike rides, or walks outside)—even a short “light shower” helps.

The timing of light is also important. Light exposure after dusk, in the hours leading up to bedtime, delays the circadian clock and alerts the brain, making it difficult to fall asleep and reducing good-quality deep sleep. After dusk, avoid bright light and choose a white light that is lacking or low in the short wavelengths for evening use, and make the light as dim as possible. Use night-dimming modes or software to reduce the light emitted by electronic devices for as long as possible before bed. Make your sleeping space as dark as possible, or use a sleep mask that covers your eyes. Light in the early morning shifts the clock earlier, and so getting up and seeing light earlier can help you keep an earlier schedule, if needed.

Regularity of light exposure is important. Keep a regular daily light exposure pattern.

Light not only influences the circadian system but also affects mood and learning, and it has a direct effect on sleep. Bright days and dark nights will help with these too!

Kids are even more sensitive to light prior to bedtime. Avoid exposing children to bright light or electronic devices as they get ready for bed.

Individuals who spend a lot of time indoors (such as in nursing homes or hospitals) will benefit from lighting systems that are bright and/or contain a lot of short-wavelength light during the daytime, as this helps to mimic outdoor lighting conditions."