The Night Mode is a change to the OS as released in the first developer preview of Android Nougat. In a similar way to Night Shift on iOS, the feature will diminish the blue light emission on the screen to warm colors ideal for nighttime view. However, you might have to enable the feature manually in Android refurbished tablets.
Firstly, enable System Tuner UI. For that, go to the Notifications Panel and tap and grab a hold of Settings icon denoted by gear icon and then let go of the hold after 10 seconds. Then, you will be lead to Settings and there you can see Congrats! System UI Tuner has been added to Settings message.
Secondly, go to Google Play Store and download and install the app Night Mode Enabler. Somehow or the other Night Mode got hidden in settings even when the full version of Nougat released following the developments. That is why you need to download Night Mode Enabler app to put the Android tablets ft. Nougat on Night Mode.
Thirdly, open the downloaded Night Mode Enabler app and then tap on the Enable Night Mode button appearing on the middle of the screen. Hang on; there is still some work to do to enable Night Mode on Nougat, as tapping on the button will take you back to System Tuner UI.
Now turn on the toggle switch of System Tuner UI and use the Adjust Brightness and Adjust Tint options to tweak the settings under When Night Mode Is On section. However, there is also an optional method to enable Night Mode on Nougat so you need not necessarily enable Night Mode when Nougat navigates you to System Tuner UI.
The warm red light will get stronger when the light stays darker outside so the optional method will help you to time the enabling of Night Mode on Nougat. For that, navigate to Quick Settings > Edit and then tap on the three dot menu button on the top right corner. Now select Reset to enable Night Mode on your Android tablet as per light on a given day. Once you put your device on Night Mode, you could spot below portion of the home screen of Android in warm red color.
A benefit of putting Android tablets on Night Mode is that the blue light emission from the device screen will not interrupt the circadian rhythm. Turn on Night Mode and experience the view on your refurbished tablets any time during the day or at night.