Although OS X Yosemite is still a few months out from public release, the public beta and developer seeds means the OS is already seeing wide adoption — hence, apps for Yosemite are already starting to surface. In fact, the unreleased OS already makes up 18% of Mac users on 9to5Mac, already the second most popular version of OS X.
As standard, Yosemite offers a dark mode that changes the look of the menubar and Dock from the stock white appearance to a black translucent material. Unfortunately, the option is quite primitive, toggled on or off by a checkbox in System Preferences. Lights Out is a neat utility by Sam Turner that adds a new preference to pane to enable Dark Mode automatically at specific times of day. This means you can set Dark Mode to turn on at night (to help with screen glare) and wake up to the brighter look the next morning, sort of like a faux-Flux.
Lights Out is free to download, so there’s no real harm in trying it. Turner admits that something like this is very unlikely to be accepted in the Mac App Store (as changing system settings in dark mode is not exposed in the public API). There is also a good chance F.lux will integrate this feature directly into their screen-dimming apps in the future, but for now Lights Out is the only option.
9to5Mac has previously reported that Yosemite will make its public debut in late October, potentially alongside some new hardware.