Before the invention of clocks, sundial was a very important instrument just as clocks are today. Today, most sundials are used for ornamental purposes, but if installed properly, can provide great pleasure in telling the time of day by connecting the earth and sun through simple mathematics. A sundial will enable us to connect to the experience of time-tellers that lived centuries ago.
Sundials use shadows cast by a gnomon onto a chart of times on the dial. Differences in global positioning need to be accounted for to read the sun dial correctly if you want to know the exact clock time.