October
October is the tenth month of the Gregorian calendar and has 31 days. In the ancient Roman calendar, it was the eighth month of the year.
Roman calendar: The system of calendars used in ancient Rome, whose forms changed from the monarchy through the empire. October’s original eighth-month position comes from an earlier Roman year.
Calendar: A system for organizing days into periods such as weeks, months, and years. October is one month within a larger system for dividing the year.
Halloween: A holiday observed on October 31, associated with costumes, trick-or-treating, and other traditions. It is October’s best-known annual observance in many countries.
September: The ninth month of the Gregorian calendar, with 30 days; its name derives from the Latin for seven. Like October, its name reflects an earlier position in the Roman calendar.
Roman numerals: A numeral system from ancient Rome that uses letters such as I, V, X, L, C, D, and M. The Latin root octo means eight, preserving October’s former calendar position.
Month: A unit of time used in calendars, usually lasting between 28 and 31 days. October is a 31-day instance of this calendar unit.
United Nations Day: An annual observance on October 24 marking the entry into force of the United Nations Charter in 1945. Its fixed date falls within October and commemorates the founding of the United Nations.
November: The eleventh month of the Gregorian calendar, with 30 days; its name derives from the Latin for nine. It follows October while retaining a Roman-derived name that no longer matches its month number.
January: The first month of the Gregorian calendar, named for the Roman god Janus. Adding January before March shifted October from the eighth position to the tenth.
Leap year: A calendar year containing an extra day to keep the calendar aligned with the solar year. Leap years add a day to February, but October always has 31 days.