Mercedonius
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Mercedonius, also known as Intercalaris, was the intercalary month added in leap years of the Roman calendar. The resulting year was either 377 or 378 days long. The exact mechanism by which this was done is not clearly specified in ancient sources. It is generally agreed by modern scholars that Februarius was truncated to 23 or 24 days, to be followed by an intercalary month of 27 days.[1] As a result, the year was lengthened by a total of 22 or 23 days. Romans believed that the month had been added to the Roman calendar, along with Ianuarius and Februarius, by King Numa Pompilius in the 7th century BC. The name Mercedonius comes from merces, meaning wages, as workers were paid at that time of year.
This month was supposed to be inserted every two or three years to align the 355-day common year with the tropical year.[2] The decision whether to insert the intercalary month was made by the pontifex maximus, supposedly based on observations to ensure the best possible correspondence with the seasons.[3] Unfortunately the pontifex maximus (whose office was generally held by a politician or soldier, notably Julius Caesar during the so-called Years of Confusion) often neglected to insert the month at the proper time, or deliberately inserted it early or late to allow some officials to stay in office longer or force others out early. Such unpredictable intercalation meant that dates following Februarius could not be known in advance; neither could the current date for citizens out of communication with the city.
The month was eliminated by Julius Caesar when he introduced the Julian calendar in 46 BC.
Notes
- ^ A.K. Michels, The Calendar of the Roman Republic (Princeton, 1967), 145-172.
- ^ "The lunar year of 354 days fell short of the solar year by 11-1/4 days;—this in 8 years amounted to 90 days. These 90 days he divided into 2 months of 22 and 2 of 23 days, and introduced them alternately every second year for two octennial periods: every third octennial period, however, Numa intercalated only [...] 3 months [...] because he adopted 355 days as the length of his lunar year"
D. Spillan, Livy's History of Rome, Book I. 19. Footnote 24.
This is the theory of Macrobius in Saturnalia (c. AD 430). - ^ "Their management was left to the pontiffs—ad metam eandem solis unde orsi essent—dies congruerent; 'that the days might correspond to the same starting-point of the sun in the heavens whence they had set out.'"
D. Spillan, Livy's History of Rome, Book I. 19. Footnote 24.