As we've mentioned, the Galaxy S8 Android Pie update comes with a brand new user interface called One UI. It looks a lot different than Samsung's Experience UI and comes with some brand new features.
Among them, Night Mode, a new feature that should help you conserve battery life and will make your device's screen easier on the eyes.
When you toggle Night Mode on you'll also notice changes across the user interface. Most stock Samsung apps including the Bixby Home UI are compatible with Night Mode.
You can manually turn Night Mode on whenever you want to use it and you should be able to automatically schedule Night Mode to turn on as well. You'll find that option in your device's display settings.
It's one of the One UI's best features and it's a feature you'll use a lot.