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 against a horizontal time line. The vertical axis is used for expansion to show separate national names for ease in charting, but otherwise has no significance. Adoption of the Gregorian calendar The adoption of the Gregorian Calendar was an event in the modern history of most nations and societies, marking a change from their traditional (or "old style") dating system to the modern (or "new style") dating system that is widely used around the world today. Some countries adopted the new calendar from 1582, some did not do so before the early twentieth century, and others did so at various