Strange but True — The Roman Year of Confusion

In ancient times, the Romans used to keep track of the days passing based on a system said to have been laid down by the founders of Rome, Romulus and Remus, in the year 738BCE. Scholars believe this system was derived from the Greek lunar calendar, which, in turn, was based on time keeping methods of the Babylonians. This ancient calendar consisted of 304 days, divided into ten months, using the eight-day week devised by the Etruscans. The remaining 61 and a half days were ignored, leaving a sizeable discrepancy during each winter. The months were named; Martius, Aprilis, Maius, Junius, Quintilis, Sextilis, September, October, November, and December.

Fragment of an ancient Roman calendar — Kleuske, CC BY-SA 3.0

The second king of Rome, Numa Pompilius (c.700BCE), added January to the beginning and February to the end of the list to help fill the gap. In 452BCE, February was moved to its final position between January and March. By 100BCE, this system was a mess. Their decision to use a lunar based system left them short by about 10¼ days per year, so periodically, they would add an extra month of around 27 or 28 days, called Mercedonius, to catch up with the changing seasons. This additional confusion was exploited by early politicians (surprise, surprise!) to increase or decrease the length of office for certain magistrates or officials.