If you have installed iOS 9.3 you may have noticed a new Night Shift option under the Display & Brightness settings. Night Shift allows you to enable your iPhone to automatically adjust the colors in your display based the night and day. The new feature uses your iOS device’s clock and geolocation to determine the time of day, and it adjusts the spectrum of your display accordingly. This allows you to sleep better at night when using your iPhone before going to bed. You can learn more about Night Shift here.
What is the purpose of Night Shift mode on my iPhone?