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
Adoption of the Gregorian calendar the old style calendars were similar but not all the same. The Arabic numerals may be used for both calendar dates in modern Japanese and Korean languages, but not for Chinese old-style dates. Japan started using the Gregorian calendar on 1 January 1873, locally known as . The preceding day, 31 December 1872, was . Japan currently uses two eras: the western era and a modified traditional Japanese era name (nengō). The months and days are those of the Gregorian calendar, but the year is either the western year number or a year of the nengō of the emperor on