This is a quick, simple, free app for your computer that adjusts your screen's color and brightness to the time of day. During daytime hours, the screen is colored to work best in sunlight, at night, the screen is tinted to warmer hues to emulate indoor lighting. The color adjustment is supposedly better on your eyes than staring at a normal monitor...especially at night.
Its free for PCs and Macs
There are similar adjustment apps for mobile devices in the App Store and pla.