December ( ) is the twelfth and last month of the year in the Julian and Gregorian Calendars. It is one of seven months with the length of 31 days. 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.