This app was mentioned in 4 comments, with an average of 2.50 upvotes
Cyanogenmod 13 on my GS4 with a mixture of Inversion UI and Neptune Material Theme
Which ROM are you using?
I've been looking for a system wide dark or night mode myself. The closest I could get is InversionUI theme, available for Layers or CM theme engines. It isn't perfect throughout all apps but does a decent job and may help depending how important this is to you. Perhaps your ROM has a similar theme.
https://play.google.com/store/apps/details?id=com.spastef.inversion
Beyond that, you can try Flipster, which essentially allows you to apply a chosen colour to any UI element of any app. Very powerful but also very involved since it's a manual step for each app. If you could apply presets for each app that other people have created, it would rock. Downside is, this is an xposed module and so needs root.
https://play.google.com/store/apps/details?id=com.arjerine.flipster
Edit: added proper links as the linkbot got it wrong
He has the same theme for CM 12.1 as well, hopefully you get some CM13 love soon.