Tomorrow is the Winter Solstice at 2:02 a.m. PST. It is the shortest day and longest night of the year. The solstice occurs when one the Earth's pole's maximum tilt is away from the sun. For the Northern Hemisphere, this happens in December and in the southern hemisphere it occurs in June. So for the U.S. (where I live), the winter solstice occurs in the wee hours of tomorrow morning.
It is the first day of Winter. And to add to the excitement, tomorrow at sunset the "Christmas Star" will be visible!