Coligny calendar

The Coligny calendar is a bronze plaque with an inscribed calendar, made in Roman Gaul in the 2nd century CE. It lays out a 5-year cycle of a lunisolar calendar, each year with 12 lunar months. An intercalary month is inserted before each 2.5 years. It is the most important piece of evidence enabling the reconstruction of an ancient Celtic calendar.

The calendar was found in 1897 in France, in Coligny, Ain (near Lyon), along with broken pieces of a life-size bronze statue of a nude male holding a spear, likely meant to portray Mars, the Roman god of war. Approximately 40% of the original calendar remains in the form of fragments. It was engraved on a bronze tablet, preserved in 73 fragments, that was originally 134.8 cm wide by 78.0 cm high. With the rim attached the plate measured 52 by 32 unciae Drusianae (2.75 cm to the uncia). It is written in the Gaulish language with the Latin alphabet, using Roman square capitals and Roman numerals. Based on the style of lettering and the accompanying statue, the bronze plaque likely dates to the end of the second century CE, although copying errors indicate that the calendar itself is much older. It is now held at the Gallo-Roman Museum of Lyon-Fourvière.

Eight small fragments of a similar calendar were found at the double-shrine of Villards-d'Héria. It does not have the holes of a peg calendar that the Coligny calendar does, but otherwise has the same notations. It is now held in the Musée d'Archéologie du Jura at Lons-le-Saunier.