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
Iunius (month) dating and observances on the following table are from H.H. Scullard, "Festivals and Ceremonies of the Roman Republic". Scullard places the Taurian Games on June 25–26 on a five-year cycle, but other scholars believe these "ludi" had no regular date and were held as a crisis ritual when needed. After the Ides, dual dates are given to represent both the earlier calendar, when June had 29 days and July was called "Quinctilis", and the 30-day month of the Julian calendar. Iunius (month) On the ancient Roman calendar, mensis Iunius or Iunius, also Junius (June), was the fourth month, following "Maius"