What a clever idea. F.lux is a freeware program that adjusts the color of your screen depending on the time of day. So at night, F.lux makes the screen look warmer and less glaringly blue than during the day. The end result is a screen that is much easier on the eyes.
F.lux works by changing the color temperature of your display. The default setting is 3400K for night and 6500K for daytime. This can affect color sensitive work such as editing digital photographs but there is a disable switch that allows you to turn F.lux off.
The change in color is automatic based on estimated sunrise and sunset times for your location. The location is only a guess based on your time zone settings but you can enter an exact latitude and longitude if you wish.
Versions are available for Windows XP/Vista/7, Mac OS X and Linux. The Windows download is 545KB.
Many thanks to Panzer for this suggestion. If you have a good freeware program or interesting website to suggest contact Gizmo using the site contact form in the left navigation sidebar.