September (Roman month) September (Roman month) September (from Latin "septem", "seven") or mensis September was originally the seventh of ten months on the ancient Roman calendar that began with March ("mensis Martius", "Mars' month"). It had 29 days. After the reforms that resulted in a 12-month year, September became the ninth month, but retained its name. September followed what was originally Sextilis, the "sixth" month, renamed "Augustus" in honor of the first Roman emperor, and preceded October, the "eighth" month that like September retained its numerical name contrary to its position on the calendar. A day was added to September in the mid-40s
Undecimber Undecimber Undecimber or Undecember is a name for a thirteenth month in a calendar that normally has twelve months. Duodecimber or Duodecember is similarly a fourteenth month. The word "undecimber" is based on the Latin word "undecim" meaning "eleven". It is formed in analogy with "December," which, though the twelfth month in the Gregorian calendar, derives from "decem" meaning "ten". The word "undecember" (abbreviated "Vnde") is recorded from a Roman inscription according to the Oxford Latin Dictionary, which defines it as "a humorous name given to the month following December". Some recent authors report the names "Undecember" and "Duodecember" for