With OS X 10.10 Yosemite, one of the new features introduced by Apple was the Dark Mode. There are two ways to activate it. You can either go to System Preferences > General and check “Use dark menu bar and dock” under “Appearance” or hit CMD+Alt(option)+Control+T. Woahhh a shorcut? Yeah, a shortcut but it won’t work just like that. To make it work, you’ll need to open the Terminal.app and type this in: /Library/Preferences/.GlobalPreferences.plist _HIEnableThemeSwitchHotKey -bool true.
Maybe the shortcut is more than enough for you, but here’s another way to activate the Dark Mode: schedule it with “Lights Out”. Download the app here, and jump over the break to check out the video on how to use it.