Martius (31 days), Aprilis (29 days), Maius (31 days), Junius (29 days), Quintilis (31 days), Sextilis (29 days), September (29 days), October (31 days), November (29 days), December (29 days), Ianuarius (29 days), Februarius (28 days)
This calendar had 360 days, but was still mismatched with the solar year of 365 days, four hours, and fifty six minutes, so an accommodation was made to add a leap month. February was shortened to twenty-four days, to produce a twenty-seven day leap month about every three years. This leap month was called the Mensis Intercalaris.