October keeps the number eight from the old March year, and like September it survived an emperor's attempt to take it, Domitian's Domitianus vanishing with his memory. In the Roman religious calendar the month closed what March had opened: the campaigning season of Mars. On the fifteenth of October a two horse chariot race was run on the Campus Martius and the right hand horse of the winning team was sacrificed to Mars, the October Horse, the only horse sacrifice in the Roman year. The inhabitants of two neighbourhoods fought for possession of the severed head, and the tail was carried at a run to the Regia so that its blood could touch the sacred hearth, a rite so archaic that Roman antiquarians already argued about what it meant. On the nineteenth the Armilustrium purified the army's weapons before they were laid up for winter, the mirror of the March rites that had readied them.
The gentler festivals of the month belonged to the harvest of the vine and the water supply: at the Meditrinalia of the eleventh the new wine was tasted with an old healing formula, and at the Fontinalia of the thirteenth the springs and wellheads of the city were garlanded with flowers, small courtesies to the powers that kept Rome alive.
Nothing in the pagan month, however, has shaped the modern October so much as a Christian vigil: the eve of All Saints, which gave the month's last night its enduring name.