The Roman calendar originally started the year with the vernal equinox and consisted of 10 months (Martius, Aprilis, Maius, Junius, Quntilis, Sextilis, September, October, November, and December) having a total of 304 days. The numbers still embedded in the last four months of the year are the fossil of this (September, October, November, and December, contain the Latin roots for the numerals seven, eight, nine, and ten,but now fall on the ninth, tenth, eleventh and twelfth months of the year). The 304 days were followed by an unnamed, unnumbered period in winter. The second Roman king Numa Pompilius (715-673 BC) introduced February and January (in that order) between December and March, increasing the length of the year to 354 or 355 days. Then in 450 BC, February was moved to its current position (Tøndering). The Roman calendar was eventually supplanted by the more rational Julian calendar in 46 BC.

Babylonian Calendar, Calendar, Egyptian Calendar, French Revolutionary Calendar, Gregorian Calendar, Islamic Calendar, Julian Calendar