"Night Shift uses your iOS device’s clock and geolocation to determine when it’s sunset in your location," the company said on its website. "Then it automatically shifts the colors in your display to the warmer end of the spectrum, making it easier on your eyes. In the morning, it returns the display to its regular settings."
It will also let you set a schedule for how you want your display to change throughout the day, if you don't want it to be automatic.
The developer beta also has some updates for Apple's Health app. The new version of the app will look more like the "Activity" app for the Apple Watch and will display how much you've moved, exercised and sat throughout the day. It will also link you to apps that will work with the health data you're viewing. According to MacRumors, the new features don't appear to be working yet.
Other changes include the ability to add password protection to the Notes app, and an improved News app that loads new content more quickly. In notes to developers, Apple said it has also added some extra 3-D Touch shortcuts to apps such as Weather and Settings.
Finally, Apple also announced that it's made some updates to CarPlay, its in-dashboard software system that lets users hook their iPhones up to their vehicles. The software will now include suggestions from Apple Music, and will also include its Nearby places suggestions. Both of these should be familiar features for iPhone users, but it's nice to see them mirrored on the in-car system. Apple, of course, recently announced that it's struck deals with Honda and Ford to support CarPlay in their upcoming models -- giving Apple a market for CarPlay that includes many of the country's top-selling models.
The company has not announced when the new system will be released to the general public, but a version of iOS 9.3 is already available on its developer site. Users should expect to see these features whenever the system launches.