October (Roman month) October (Roman month) October (from Latin "octo", "eight") or mensis October was the eighth of ten months on the oldest Roman calendar. It had 31 days. October followed September (from "septem", "seven") and preceded November ("novem", "nine"). After the calendar reform that resulted in a 12-month year, October became the tenth month, but retained its numerical name, as did the other months from September through December. Some of the observances in October marked the close of the season for military campaigning and farming, which commenced in March ("Martius", "Mars' month"). October was under the guardianship "(tutela)" of Mars. The Romans
Adoption of the Gregorian calendar Japan decided to officially replace its traditional lunisolar calendar with the Gregorian calendar in 1872, so the day following the second day of the twelfth month of the fifth year of the Meiji emperor's rule, became . (The Japanese rendering of the Western months is simply "ichi-gatsu" or "One-month" for January, "ni-gatsu" or "Two-month" for February, etc.) This brought Japan's calendar in alignment with that of the major Western powers (excluding Russia). To this day, however, it is common to use Nengo, reign names instead of the Common Era or Anno Domini system, especially for official documents; for instance, "Meiji"