Roman calendar

The Roman calendar changed its form several times between the founding of Rome and the fall of the Roman Empire. The common calendar widely used today is known as the Gregorian calendar and is a refinement of the Julian calendar where the length of the year has been adjusted from 365.25 days to 365.2425 days (a 0.002% change).

From at least the period of Augustus on, calendars were often inscribed in stone and displayed publicly. Such calendars are called fasti.

History

The original Roman calendar is believed to have been a lunar calendar, which may have been based on one of the Greek lunar calendars. As the time between new moons averages 29.5 days its months were constructed to be either hollow (29 days) or full (30 days).

Calendar of Romulus

Roman writers attributed the original Roman calendar to Romulus, the mythical founder of Rome, though there is no other evidence for the existence of such a calendar and Romulus was often cited as the founder of practices whose origins were unknown to later Romans. According to these writers, Romulus' calendar had ten months with the spring equinox in the first month (likely based on the names of the last months of the year):