This drawing fills in a fragmentary fresco that was found in the ruins of Nero's villa at Antium. It depicts the pre-Julian Roman calendar. The months January to December and the leap month Intercalaris are listed across the top.
Each side bears the names of free months of the year. For each month we can see starting from the top : the number of days in it, the day in which the Nones (the day of the moons first quarter) falls; the duration of the day.