When the Roman months began on the new moon, the ides of March would have fallen on a full moon.
Ovid in Fasti mentions the procession of Anna Perenna on this day, in which a drunken old woman known as the Petreia, is dragged along the streets by a drunken old man, who may represent Mamurius Veturis. Both of these figures seem to represent the old year, much like modern American depictions of Grandfather Time on New Year’s Eve.
Anna Perenna is a goddess of annual return. In one legend, Mars asks her to help him seduce Minerva but she takes Minerva’s place and then mocks the god when he recognizes her. This accounts for the bawdy songs sung at her festival.
The common people of Rome picnicked in a grove and amused themselves by singing, dancing and drinking a cup of wine for each year of one’s age. Obviously the tradition of getting drunk on St. Patrick’s Day (or near the equinox) has ancient roots.
Blackburn, Bonnie and Leofranc Holford-Strevens, Oxford Companion to the Year, Oxford University Press 1999