December (Roman month) December (Roman month) December (from Latin "decem", "ten") or mensis December was originally the tenth month of the Roman calendar, following November ("novem", "nine") and preceding Ianuarius. It had 29 days. When the calendar was reformed to create a 12-month year starting in Ianuarius, December became the twelfth month, but retained its name, as did the other numbered months from Quintilis (July) through December. Its length was increased to 31 days under the Julian calendar reform. The Romans did not number days of a month sequentially from the first day through the last. Instead, they counted back from the three
September (Roman month) BC as part of the Julian calendar reform. September has none of the archaic festivals that are marked in large letters for other months on extant Roman "fasti". Instead, about half the month is devoted to the "Ludi Romani", "Roman Games", which developed as votive games for Jupiter Optimus Maximus ("Jupiter Best and Greatest"). The "Ludi Romani" are the oldest games instituted by the Romans, dating from 509 BC. On the Ides of September (the 13th), Jupiter was honored with a public banquet, the "Epulum Jovis". A nail-driving ritual in the temple marked the passing of the political year during