Roman calendar

The Roman calendar was used by the Roman Kingdom and Roman Republic. Although the term is primarily used for Rome's pre-Julian calendars, it is often used inclusively of the Julian calendar established by Julius Caesar in 46 BC. According to most Roman accounts, their original calendar was established by their legendary first king Romulus. It consisted of ten months, beginning in spring with March and leaving winter as an unassigned span of days before the next year. These months each had 30 or 31 days and ran for 38 nundinal cycles, each forming a kind of eight-day week—nine days counted inclusively in the Roman manner—and ending with religious rituals and a public market. This fixed calendar bore traces of its origin as an observational lunar one. In particular, the most important days of each month—its kalends, nones, and ides—seem to have derived from the new moon, the first-quarter moon, and the full moon respectively. To a late date, the College of Pontiffs formally proclaimed each of these days on the Capitoline Hill and Roman dating counted down inclusively towards the next such day in any month. (For example, the year-end festival of Terminalia on 23 February was called VII. Kal. Mart., the 6th day before the March kalends.) Romulus's successor Numa Pompilius is usually credited with a revised calendar that divided winter between the two months of January and February, shortened most other months, and established rough alignment with the solar year by some system of intercalation. This is a typical feature of lunisolar calendars and was necessary to keep the Roman religious festivals and other activities within their proper seasons. Modern historians dispute various points of this account. It is possible the original calendar was agriculturally based, observational of the seasons and stars rather than of the moon, with ten months of varying length filling the entire year. If this ever existed, it would have changed to the lunisolar system later credited to Numa during the kingdom or early Republic under the influence of the Etruscans and of Pythagorean Southern Italian Greeks. After the establishment of the Republic, years began to be dated by consulships but the calendar and its rituals were otherwise very conservatively maintained until the Late Republic. Even when the nundinal cycles had completely departed from correlation with the moon's phases, a pontiff was obliged to meet the sacred king, to claim that he had observed the new moon, and to offer a sacrifice to Juno to solemnize each kalends. It is clear that, for a variety of reasons, the intercalation necessary for the system's accuracy was not always observed. Astronomical events recorded in Livy show the civil calendar had varied from the solar year by an entire season in 190 BC and was still two months off in 168 BC. By the 191 BC Lex Acilia or before, control of intercalation was given to the pontifex maximus but—as these were often active political leaders like Caesar—political considerations continued to interfere with its regular application. Victorious in his civil war, Caesar reformed the calendar in 46 BC, making the year of his third consulship last for 446 days. This new Julian calendar was an entirely solar one, influenced by the Egyptian calendar. In order to avoid interfering with Rome's religious ceremonies, the reform distributed the unassigned days among the months (towards their ends) and did not adjust any nones or ides, even in months which came to have 31 days. The Julian calendar was designed to have a single leap day every fourth year by repeating February 24 (a doubled VI. Kal. Mart. or ante diem bis sextum Kalendas Martias) but, following Caesar's assassination, the priests mistakenly added the bissextile (bis sextum) leap day every three years due to their inclusive counting. In order to bring the calendar back to its proper place, Augustus was obliged to suspend intercalation for one or two decades. At 365.25 days, the Julian calendar remained slightly longer than the solar year (365.24 days). By the 16th century, the date of Easter had shifted so far away from the vernal equinox that Pope Gregory XIII ordered a further correction to the calendar method, resulting in the establishment of the modern Gregorian calendar.

History

Prehistoric calendar The original Roman calendar is usually believed to have been an observational lunar calendar whose months ended and began from the new moon. Because a lunar cycle is about 29.5 days long, such months would have varied between 29 and 30 days. Twelve such months would have fallen 10 or 11 days short of the solar year and, without adjustment, such a year would have quickly rotated out of alignment with the seasons in the manner of the Islamic calendar. Given the seasonal aspects of the calendar and its associated religious festivals, this was presumably avoided through some form of arbitrary curtailment or intercalation or through the suspension of the calendar during winter. Against this, Michels has argued that the early calendars used by Rome and its neighbors were more probably observational of seasonal markers in nature (the leafing of trees), animal behavior (the migration of birds), and the agricultural cycle (the ripening of grain) combined with observation of stars in the night sky. She considers that this more sensibly accounts for later legends of Romulus's decimal year and the great irregularity in Italian month lengths recorded in Censorinus. Roman works on agriculture including those of Cato, Varro, Vergil, Columella, and Pliny invariably date their practices based on suitable conditions or upon the rising of stars, with only occasional supplementary mention of the civil calendar of their times until the 4th or 5th century author Palladius. Augury, formal Roman ornithomancy, continued to be the focus of a prestigious dedicated priesthood until at least the end of the 4th century. Although most Roman festivals in the historical record were closely tied to the nundinal cycle of the later calendar, there remained several moveable feasts (feriae conceptivae, "proclaimed festivals") like the Sementivae that were dependent on local conditions. Michels suggests this was the original state of all ancient festivals, marking divisions between the seasons and occasions within them.

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