December is the first month of meteorological winter in the Northern Hemisphere and in the Southern Hemisphere is the first month of summer. December is the month with the shortest daylight hours of the year in the Northern Hemisphere and the longest daylight hours of the year in the Southern Hemisphere.
December, from the Très Riches Heures du duc de Berry
December gets its name from the Latin word decem (meaning ten) because it was originally the tenth month of the year in the Roman calendar, which began in March. The winter days following December were not included as part of any month. Later, the months of January and February were created out of the monthless period and added to the beginning of the calendar, but December retained its name.