With Night Shift mode, when the sun goes down, the iPhone or iPad's screen will automatically change towards the warmer (yellower) colors in the spectrum, reducing blue light. In the morning, the display returns to its normal temperature color, mimicking natural light. Night shift can be set to come on when the sun sets or it can be toggled on with a Control Center button.
Night Shift is available on all iOS devices that have an A7 or later processor. This includes the iPhone 5s and later, the iPad mini 2 and later, the iPad Air and later, the iPod touch 6G, and the iPad Pro.