December -- the tenth month

December had 30 days, until Numa when it had 29 days, until Julius when it became 31 days long. Sources These sources are somewhat inconsistent. I have chosen interpretations that are predominate among sources or that seem most reasonable.

William Morris, editor, The American Heritage Dictionary of the English Language , New College Edition, Houghton Mifflin Company, Boston, 1976

Webster's Encyclopedic Unabridged Dictionary of the English Language , Portland House, New York, 1989

William Matthew O'Neil, Time and the Calendars , Sydney University Press, 1975 See Also The Royal Greenwich Observatory provides information on time, the calendar, the date of Easter, the equation of time, leap years, and the year 2000 AD.

The United States Naval Observatory has several systems of time.