February

The Roman month Februarius was named after the Latin term februum, which means purification, via the purification ritual Februa held on February 15 (full moon) in the old lunar Roman calendar. January and February were the last two months to be added to the Roman calendar.

At certain intervals February was truncated to 23 or 24 days, and a 27-day intercalary month.

Under the reforms that instituted the Julian calendar, Intercalaris was abolished, leap years occurred regularly every fourth year, and in leap years February gained a 29th day. Thereafter, it remained the second month of the calendar year, meaning the order that months are displayed (January, February, March, ..., December) within a year-at-a-glance calendar. The Gregorian calendar reforms made slight changes to the system for determining which years were leap years and thus contained a 29-day February.