With the days getting increasingly shorter and colder, it may appear as though winter has been upon us for many weeks. However, though meteorologists in the Northern Hemisphere consider December 1 as the start of the season, according to the astronomical calendar, the season will not begin until Friday, December 21. Often referred to as winter solstice, it is also the shortest day and longest night of the year. Southern Hemisphere residents, on the other hand, will celebrate summer solstice, the start of the astronomical summer, with the longest day and shortest night of 2018.