Until the invention of the mechanical clock, daily solar timekeeping was a straightforward affair: basically you just stuck a pole in the ground and marked where the shadow landed. There was no concept of a fixed time structure. Sunrise, noon, and sunset marked the day; whatever gradations existed in between were customary, not universal. For the most part, people did not keep rigid appointments through the day as we now do.

Then, with the arrival of inflexible time, came the realization that the length of the day, noon-to-noon, is not a constant 24 hours, but changes a bit every day in a year-long pattern. So attempts to create simple solar timepieces, sundials, that could show clock time were doomed to failure, since the angle of the sun at a given clock time is always changing through the year - not just north/south from Winter to Summer - but also from east to west.

This disconnect between clock time and solar time is known as the "Equation of Time", or by its visual manifestation, the Analemma. It's that strange figure-eight shape that used to be on every globe of the Earth; it represents the sun's apparent deviation from a straght north-south path as it moves from one solstice to the other.

If you stick a pole in the ground and go out every day at precisely noon by your clock (keeping to Standard time all year) and mark the tip of the pole's shadow on the ground, at the end of the year you will have created an analemma, and thereafter can tell when it's noon local (Standard) time by the Sun! You will have created a simple solar clock which is 100% accurate, every day, at noon.

Practical Sundials is software that reins in that wild Sun shadow. It can generate an analemma clock on demand, with an analemma for each hour through the day, for any location on Earth. The result can be used as a wall decoration, a working sundial clock, an educational resource, or even enlarged to architectural scale.