light
f.lux: software to make your life better
see also
Alfred is for OS X and a fantastic utility for automation, I don’t know if there is a similar widget for non-Mac environments or not.
Hexagram 24: Fu (The Turning Point)

The idea of a turning point arises from the fact that after the dark lines have pushed all of the light lines upward and out of the hexagram, another light line enters the hexagram from below. The time of darkness is past. The winter solstice brings the victory of light. This hexagram is linked with the eleventh month, the month of the solstice (December-January). deoxy.org