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 five-year cycle of a lunisolar calendar, each year with twelve lunar months. An intercalary month is inserted before each 2.5 years. The lunar phase is tracked with exceptional precision, adjusted when necessary by a variable month, and the calendar uses the 19-year Metonic cycle to keep track of the solar year. It is the most important evidence for the reconstruction of an ancient Celtic calendar.

It was found in 1897 in France, in Coligny, Ain (46°23′N 5°21′E / 46.383°N 5.350°E / 46.383; 5.350, near Lyon), along with broken pieces of a bronze statue of a life-size naked male holding a spear, likely Roman Mars or Romano-Celtic Lugus.^[1] It was engraved on a bronze tablet, preserved in 73 fragments, that was originally 1.48 metres (4 ft 10 in) wide by 0.9 metres (2 ft 11 in) tall, equivalent to 5 x 3 Roman feet. It is written in Latin inscriptional capitals and numerals, but terms are in the Gaulish language. Based on the style of lettering and the accompanying statue, the bronze plaque probably dates to the end of the second century, although the copying errors indicate the calendar itself is much older. ^[2] 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^[3] 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.