Sundials have been widely used by people beginning from the earliest civilizations until the later part of the 19th century, when the worlds time zones were established. Before this, people relied exclusively on local solar time.
Sundials are loosely derived from obelisks and shadow clocks used by humans earliest known civilizations to measure time. Obelisks, in their most simple form, were used to indicate noon, thus allowing ancient peoples to divide their days into morning and afternoon. Eventually markers were drawn around the obelisks to indicate passing hours. Over time, slightly more elaborate and accurate t-shaped shadow clocks were used. These were oriented towards the east during morning hours, and manually turned to the west to track afternoon hours.
Fairly common features found in ancient structures were vertically mounted sundials against an outer building wall. These were fairly simple to set up and could be seen from afar. These vertically oriented sundials consisted of a metal gnomon, (or shadow casting indicator,) and the sundial positions painted on or set in stone on the outer wall. Unfortunately due to the cycle of seasons, these vertically mounted time pieces would only work for a portion of the year.
Over time, more elaborately engineered and accurate time-telling devices were conceived, such as equatorial sundials. Eventually, very precise sundials known as heliochronometers were developed. Among the most simple, yet accurate sundials are the equatorial bow sundials similar to the armillary sundials seen on our site. Large scale versions of this equatorial bow sundial shape are considered to be the most accurate sundials ever created & can tell time accurately to within about one minute. Similar equatorial bow sundials were used throughout France as a way to keep trains running on schedule.
Current garden sundials revive old traditions by combining a numbered disc with the shadow casting gnomon. These are designed to be set with the dial oriented horizontally, yet still keep fairly accurate solar time throughout the seasons. Today, garden sundials are used primarily as ornamental pieces and are not considered accurate time-keeping devices.