The months of September through December take their names from Latin words for seven through ten.

The longer version

Latin numerals survive inside the calendar. September, October, November and December come from the words for seven, eight, nine and ten, because they were originally the seventh through tenth months of a year that began in March. The names stuck even after the year was shifted forward by two months.

So the labels no longer match the positions: the ninth month carries the name of the seventh. Similar mismatches appear elsewhere, since many languages keep older seasonal names for months that no longer fall in that season. Readers who notice the discrepancy usually assume the names were assigned carelessly, when in fact the ordering simply predates the change.

Where this entry sits

These facts wander through clocks, calendars, time zones, and the long human effort to measure passing hours. You will find leap years, odd month lengths, ancient sundials, and the reasons modern timekeeping works the way it does. The full list sits on the Time and Calendars page, where every entry is listed in order.