It would have been the first day of Bacchanalia in ancient Rome today. The Bacchanalia were Roman festivals of Bacchus, the Greco-Roman god of wine, freedom, intoxication and ecstasy. They were based on the Greek Dionysian mysteries, and like all mystery cults, the Bacchanalia were held in strict privacy, and initiates were bound to secrecy. Apparently, five night-time cult meetings took place a month, open to all social classes, ages and sexes featuring wine-fuelled violence and sexual promiscuity, in which the screams of the abused were drowned out by the din of drums and cymbals. It was later officially suppressed.

Source: Prehistoric Shamanism