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".
Roman use
Some modern authors, including the
World Calendar Association
and
Isaac Asimov 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. This claim has no contemporary evidence;
Cicero refers to the months as "
intercalates prior and
intercalates posterior" in his letters.
Historian Cassius Dio tells that Licinus, procurator of Gaul, added two months to the year 15 BC, because taxes were paid by the month.[, 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.]
Computing
In the Java Platform, Standard Edition, the java.util.Calendar class includes support for calendars which permit thirteen months.
[
] Although the Gregorian calendar used in most parts of the world includes only twelve months, there exist some
that are divided into
, with an intercalary or "leap" month added in some years. For example, in the
Hebrew calendar seven years out of every nineteen (37%) have the "embolismic month"
Adar I.
The constant java.util.Calendar.UNDECIMBER represents such a month.
Accounting
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.
See also
-
4–4–5 calendar
-
Accounting period
-
December 32
-
February 29
-
Mercedonius
-
Ophiuchus (astrology)
