The earliest sundials known from the archaeological finds are the shadow clocks (1500 BC) in ancient Egyptian astronomy and Babylonian astronomy. Not, as incorrectly suggested, obelisks at the temples only serving as a memorial in honor of the pharaoh to whom it was devoted.^[1] Presumably, humans were telling time from shadow-lengths at an even earlier date, but this is hard to verify. In roughly 700 BC, the [Old Testament] describes a sundial — the "dial of Ahaz" mentioned in Isaiah 38:8 and II Kings 20:9 (possibly the earliest account of a sundial that is anywhere to be found in history) — which was likely of Egyptian or Babylonian design. Sundials are believed to have existed in China since ancient times, but very little is known of their history.^[2] There is an early reference to sundials from 104 BCE in an assembly of calendar experts.^[3]

Hemispherical Greek sundial from Ai Khanoum, Afghanistan, 3rd-2nd century BCE.

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 BC. According to Herodotus, the Greeks sundials were initially derived from the Babylonian counterparts. The Greeks were well-positioned to develop the science of sundials, having founded the science of geometry, and in particular discovering the conic sections that are traced by a sundial nodus. The mathematician and astronomer Theodosius of Bithynia (ca. 160 BC-ca. 100 BC) is said to have invented a universal sundial that could be used anywhere on Earth.

The Romans adopted the Greek sundials, and the first record of a sun-dial in Rome is 293 BC according to Pliny.^[4] Plautus complained in one of his plays about his day being "chopped into pieces" by the ubiquitous sundials. Writing in ca. 25 BC, the Roman author Vitruvius listed all the known types of dials in Book IX of his De Architectura, together with their Greek inventors.^[5] All of these are believed to be nodus-type sundials, differing mainly in the surface that receives the shadow of the nodus.

• the hemicyclium of Berosus the Chaldean: a truncated, concave, hemispherical surface
• the hemispherium or scaphe of Aristarchus of Samos: a full, concave, hemispherical surface
• the discus (a disc on a plane surface) of Aristarchus of Samos: a fully circular equatorial dial with nodus
• the arachne (spiderweb) of Eudoxus of Cnidus or Apollonius of Perga: half a circular equatorial dial with nodus
• the plinthium or lacunar of Scopinas of Syracuse: an example in the Circus Flaminius)
• the pros ta historoumena (universal dial) of Parmenio
• the pros pan klima of Theodosius of Bithynia and Andreas
• the pelekinon of Patrocles: the classic double-bladed axe design of hyperbolae on a planar surface
• the cone of Dionysodorus: a concave, conical surface
• the quiver of Apollonius of Perga
• the conarachne
• the conical plinthium
• the antiboreum: a hemispherium that faces North, with the sunlight entering through a small hole.

The Romans built a very large sundial in 10 BC, the Solarium Augusti, which is a classic nodus-based obelisk casting a shadow on a planar pelekinon.^[6]

The Greek dials were inherited and developed further by the Islamic Caliphate cultures and the post-Renaissance Europeans. Since the Greek dials were nodus-based with straight hour-lines, they indicated unequal hours — also called temporary hours — that varied with the seasons, since every day was divided into twelve equal segments; thus, hours were shorter in winter and longer in summer. The idea of using hours of equal time length throughout the year was the innovation of Abu'l-Hasan Ibn al-Shatir in 1371, based on earlier developments in trigonometry by Muhammad ibn Jābir al-Harrānī al-Battānī(Albategni). Ibn al-Shatir was aware that "using a gnomon that is parallel to the Earth's axis will produce sundials whose hour lines indicate equal hours on any day of the year." His sundial is the oldest polar-axis sundial still in existence. The concept later appeared in Western sundials from at least 1446.^[7][8]

The custom of measuring time by one's shadow has persisted since ancient times. In Aristophanes' play, Assembly of Women, Praxagora asks her husband to return when his shadow reaches 10 feet (3.0 m). The Venerable Bede is reported to have instructed his followers in the art of telling time by interpreting their shadow lengths.