Night Shift is the iPhone function introduced in iOS 9 that changes the colour balance of the screen as the sun sets. It makes it easier on the eyes and stops the glare of a bright screen at night.
Apple's trademark filing protects its use of the name Night Shift on devices other than the iPhone. That means that it could be planning to bring the technology to devices like the Mac range, as well as the Apple Watch.
There's already a program that changes the colour balance of a Mac as the sun sets, but it's not an official Apple product. F.lux is a free app for Macs that was released long before Night Shift on the iPhone. It has been downloaded over 15 million times. The app's founders tried to release their program on the iPhone but Apple blocked them from doing so. Months later, Apple released its official version.