This article explains how to use Night Light on an Android smartphone (running Android 8.0 and 9.0) and the Blue Light Filter on a Samsung Galaxy smartphone (running Android 7 or later).
You can set Android's Night Light feature on a schedule or turn it on and off manually.
Go to Settings > Display > Night light.
On the Night Light screen, you can set a schedule, adjust the start and end time, adjust the intensity (if Night Light is enabled), and turn the mode on or off.