Name for a thirteenth month in a calendar that normally has twelve months
Undecimber or Undecember is a name for a thirteenth month in a calendar that normally has twelve months.
Etymology
The word undecimber is based on the Latin word undecim meaning "eleven". It is formed in analogy with December, which, though the twelfth month in the Gregorian calendar, derives from decem meaning "ten". The Oxford Latin Dictionary defines it as "a humorous name given to the month following December".[1]Undecember (abbreviated Unde) appears in a Roman inscription from Vercellae in Cisalpine Gaul, dating between the first century BC and the first century AD.[2][1]
Some recent authors have reported the names "Undecember" and "Duodecember" for the two intercalary months inserted between November and December upon the adoption of the Julian calendar in 44 BC, including the World Calendar Association[3] and Isaac Asimov.[4] This claim has no contemporary evidence; Cicero refers to the months as "intercalates prior and intercalates posterior" in his letters.[5]
Historian Cassius Dio tells that Licinus, procurator of Gaul, added two months to the year 15 BC, because taxes were paid by the month.[6] Though not named by Dio, who wrote in Greek, August Immanuel Bekker suggested these might have been called "Undecember" and "Duodecember".[7]
In accounting, a thirteenth month is sometimes used to adjust financial statements for an entire year without affecting monthly results. For example, an organization may wish to adjust its books to reflect the fact that some of its sales and resulting payments due from customers will not be paid. If an organization only does this once per year the organization can attribute these adjustments to "Month 13" so as not to inaccurately post a full year's worth of write offs to one month.[11]
^ abGlare, P.G. (2002). Oxford Latin Dictionary. Clarendon Press. ISBN0-19-864224-5.
^AE1989, 331, dating an event to the eleventh day before the Kalends of Undecember. In the Julian Calendar this corresponds to December 22; in the pre-Julian calendar, with twenty-nine days in December, it would have been December 20.
^Jézéquel, Jules (1937). "Why the World Needs This Reform". Journal of Calendar Reform. 7. New York City: World Calendar Association: 64.