Equation of Time 均時差

sun time vs clock time

 

 

it is due to 

i) the plane of the Equator is not the same as the plane of the Earth's orbit around the sun, but is offset from it by the angle of obliquity, and

ii) the orbit of the Earth around the sun is an ellipse and not a circle, and the apparent motion of the sun is thus not exactly equal throughout the year.

  Positive values when a sundial appears faster compared to a clock showing local mean time; negative when slower

 

sundials uk

oarval

wiki 

usno navy mil archive

codeproject in c#

wikipedia