For all late night coders:
The program "redshift" changes your monitors' white balance according to your position on the planet and your local time. This is supposed to put less strain on your eyeballs than staring at a "daylight white" screen all day and night.
The program is in the Ubuntu repositories, so a simple "sudo apt-get install gtk-redshift" transfers it onto your hard drive.
I find the effect rather pleasing and so I have set the following alias on my computer:
alias rdshft='gtk-redshift -l 48.3714407:10.8982552 -t 6500:4200 &'
The coordinates given here are for Augsburg/Germany and the color temperatures can be set according to taste.
For WIndows and Mac users, there is f.lux which is also available for Linux. I just prefer redshift because of the simple installation.