Night Shift automatically shifts the colors of your display to the warmer end of the color spectrum after dark.
Studies have shown that exposure to bright blue light in the evening can affect your circadian rhythms and make it harder to fall asleep. Night Shift uses your computer's clock and geolocation to determine when it's sunset in your location. It then automatically shifts the colors in your display to the warmer end of the spectrum. In the morning it returns the display to its regular settings.
From the Apple menu , choose System Settings (or System Preferences).
Click Displays.
Click Night Shift. This option is available only on Mac computers that support Night Shift.
From here you can take these actions:
Create a custom Night Shift schedule, or schedule Night Shift to turn on automatically from sunset to sunrise.
Manually turn Night Shift off or on until sunrise or the scheduled time.
Make the color temperature more or less warm when Night Shift is on. Warmer color temperatures show more yellow and less blue.
Night Shift requires macOS Sierra 10.12.4 or later and is available on Mac computers introduced in 2012 or later, as well as Mac Pro computers introduced in 2013 or later. Night Shift performance on external displays depends on the characteristics of the display.
If your Appearance setting is set to Auto, your Mac switches appearance from light to dark based on the Night Shift schedule you set: When Night Shift is on, the appearance is dark.