Little tool to set the monitor brightness/gamma/color according to the time and date, Windows only.
My home page provides a binary for the sun simulator, which can just be started.
When the sun simulator is started it will automatically adjust the screen settings and add itself to the autostart list.
However, although it allows very precise, manual control over gamma/brightness/contrast settings for each of the red/green/blue channels, the default settings do not actually match the real sun. So you should set it to the values you prefer, which can done visually by adjusting the points in the interpolation graph.