The Coligny calendar was discovered in Coligny, France (near Lyon) as little more than a pile of bronze fragments in 1897 – most likely smashed by Roman authorities during the suppression of druidic practice – and painstakingly restored piece by piece. It was originally the size of a rather cramped doorway. Less than half of the calendar remains, but there is enough to clearly see a beautiful time-keeping system that aligned the sun and moon into a single calendar, and listed dozens of holidays, rituals, celebrations, and the like.
There are lots of disagreements about the calendar. For example, although everyone agrees that it effectively tracks both the sun and the moon, it’s uncertain whether months began at the new moon, the full moon, or perhaps the first quarter. In this article, I’m going to state as fact many things that are in contention, because filling the article with equivocations would turn it into a scholarly work, not a philosophical one. For example: I’m going to say that the months begin on the new moon, because in my opinion, that squares best with the evidence.