The feature itself was shown to us in Android M, then it was not when finally we know the version was Android N. After all the feature is here anyway.
However Google set the Night Mode hidden inside the system UI Tuner. To make Night Mode comes to appear take executing adb command.
People don't realize its existence until a third pary developer namely Michael Evans comes out with an Android app, namely Night Mode Enabler, that frees us from dealing with adb.
Night Mode enabler is a free app and doesn't require root access.
After you install the Night Mode Enabler app and launch it, you will be told to enable System UI Tuner (If you haven't before) by long-tap on the Settings gear on notification shade.
Once you've done you will see a button; Enable Night Mode on blank page.
You need to tap on it, then you'll be brought to the System UI Tuner, there you will find Night Mode toggle with other options to adjust tint and brightness.
But some users don't get that luck for they see no Night Mode at all or the feature just disapear after they quit using it.
And how about you? Did you able to make the Android N Night Mode enabled and keep it sticks each you reboot your device? Share to me your experiences.