The ancient Greeks developed many of the principles and forms of the sundial. Sundials are believed to have been introduced into Greece by Anaximander of Miletus, c. 560 BCE. The Greeks were more than skilled in developing the science of sundials, having founded the science of geometry, and in particular discovering the conic sections that are traced by a sundial nodus. Each sundial is divided into 12-hour sections, indicating time and corresponding to the 12 Main Gods of the Greek Pantheon.
Hemispherical Greek sundial fron Ai- Khanoum, Afghanistan. 3rd- 2nd century BCE.
EDITED FROM: Wikipedia