The Gaulish Coligny calendar is the oldest known Celtic solar-lunar ritual calendar. It was discovered in Coligny, France, and is now on display in the Palais des Arts Gallo-Roman museum, Lyon. It dates from the end of the second century CE, when the Roman Empire imposed the use of the Julian Calendar in Roman Gaul. The calendar was originally a single huge plate, but it survives only in fragments. It is inscribed in Gaulish with Latin characters and uses Roman numerals.