How to enable One UI (Android 9 Pie) dark mode on Samsung Galaxy phones
Samsung’s software has provided comprehensive theme capabilities for years but has never had a system-level dark mode like many competitors. Its Android 9 Pie software, which brings the new “One UI” interface, introduces a brand new “Night mode” that accomplishes the same goal: black out as much of the interface as possible, which is easy on your eyes at night but also friendly to your battery. This is how you enable and configure it.
How to enable dark mode on Samsung Galaxy phones with One UI (Android 9 Pie)