How to Enable the Hidden ‘Night Mode’ Setting on Android 7 …

When Google released the first Developer Preview build of Android 7.0 Nougat, users were happy to see that a new “Night Mode” was included among the changes. The feature would cancel out any blue light emitted from your screen to help you get to sleep a bit earlier, quite similar to f.lux for desktop computers, or Apple’s Night Shift for iPhones.

https://android.gadgethacks.com/how-to/enable-hidden-night-mode-setting-android-7-0-nougat-0173311/