http://en.wikipedia.org/wiki/Equation_of_time
http://en.wikipedia.org/wiki/Solar_time
Improve, perhaps by breaking into: Solar Dar, Solar Day and Noon in Sky, Equation of Time, Analemma <-> Clock and Solar Time
More or less analemma here/later?
Base of equation of time graph from http://www.nwfsc.edu/sundial/images/figure5.jpg