October (Roman month) did not number days of a month sequentially from the 1st through the last day. Instead, they counted back from the three fixed points of the month: the Nones (5th or 7th), the Ides (13th or 15th), and the Kalends (1st) of the following month. The Nones of October was the 7th, and the Ides was the 15th. The last day of October was the "pridie Kalendas Novembris," "day before the Kalends of November". Roman counting was inclusive; October 9 was "ante diem VII Idūs Octobris", "the 7th day before the Ides of October," usually abbreviated "a.d. VII Id. Oct."
September (Roman month) holidays. Unless otherwise noted, the dating and observances on the following table are from H.H. Scullard, "Festivals and Ceremonies of the Roman Republic" (Cornell University Press, 1981), pp. 96–115. After the Ides, dates are given for the 30-day month of the Julian calendar; pre-Julian dates of festivals are noted parenthetically. September has a concentration of imperial birthdays "(dies natales)": Aurelian on the 9th, Trajan on the 18th, Antoninus Pius on the 19th, and Augustus on the 23rd. Inscriptions throughout the Empire record religious dedications made on these days, often by military personnel. The Genius of "Legio II Italica Pia", an