https://www.techradar.com/news/android-p-beta-features-battery-saving-dark-mode-after-all

When it comes to implementing a dark theme in Android P that’s more friendly to battery life, Google seems to be against it for now. Or at least, that’s what we initially thought.

To the contrary of reports that a display mode that switches white user interface elements for black ones was supposedly in the works, then wasn’t, we’ve found it in decent working order in the Android P beta.