Can a sundial really tell the correct time?

"I am a sundial, and I make a botch
Of what is done far better by a watch"

So wrote Hilaire Belloc, but is this really fair? Sundials are the earliest known form of time-keeping having been used for some five thousand years. The Greek historian Herodotus stated that sundials were first used by the Chaldeans and Sumerians in Babylonia which was part of the modern Iraq. They used vertical rods on their buildings and noted the position of the shadow to record the passing of the hours. The concept was developed by the Greeks and Romans who constructed various different shapes of dial to enable them to tell the time and the season of the year. Usually these were bowl-shaped dials with vertical or horizontal gnomons (shadow-casters) and hour lines marked in the hollow of the bowl. Over the years more elaborate designs were produced until the advent of accurate clocks when the function of the sundial became more decorative than as a reliable means of telling the time. Read more...