December is the twelfth and final month of the year in the Julian and Gregorian calendars. It is also the last of seven months to have a length of 31 days. December got its name from the Latin word decem (meaning ten) because it was originally the tenth month of the year in the calendar of Romulus c. 750 BC, which began in March. The winter days following December were not included as part of any month. Later, January and February were created out of the months period and added to the beginning of the calendar, but December retained its name.

Months of the Year

A month is a unit of time used with calendars, which is approximately as long as a natural period related to the motion of the Moon; month and Moon are cognates. The traditional concept arose with the cycle of moon phases; such months (lunations) are synodic months and last approximately 29.53 days. Researchers have deduced that people counted days in relation to the Moon's phases from excavated tally sticks as early as the Paleolithic age.