CSM alumnus, Scot Swan, offers Sundials_and_Linear_Algebra,  which is a short (informal) writeup on the equations that are used for making standard horizontal dials.   Challenge: see if Scot’s write up is consistent with the calculator at http://www.anycalculator.com/horizontalsundial.htm.

Here are more fun images from geeks like Scot:

Sunclock landscaping!

Geek clock