The winter solstice, also known as the first day of winter in the Northern Hemisphere, marks the shortest day and longest night of the calendar year. This year, it falls on Saturday, December 21, 2019, in the U.S. (but December 22 in other time zones) when the sun reaches its lowest point in the sky and the North Pole is tilted furthest from the sun.
https://www.countryliving.com/life/a25644318/winter-solstice-facts-celebrations/

