F.lux is software to automatically adjust the colour of your computer screen to warmer colours as the sun sets.
This gradual change feels a lot softer on the eyes in the evening, and it supposedly also reduces the amount of blue light that you get. This is important, because your eyes receiving blue light sabotages your body from generating melatonin, and hence making it hard to get to sleep.
I have F.lux on all but one of my computers*, as it runs on MacOS, Windows, and Linux. You can also to run it on on Android and jailbroken iOS devices (however, starting iOS 9.3 Apple has introduced Night Shift, that does something similar).
I highly advice installing it on all your devices, if only because the candle-light colour is really nice on the eyes too.
*I have not installed it on my dedicated game and graphics machine, as I don’t play on the evenings and want nothing to interfere with the graphics.