Winter Solstice began December 21, 2009 @ 17:55 Greenwich Mean Time. If you're like most Americans, you have no idea what time that is in your household - so check the World Times Zones site.
The solstice is either of the two times a year when the Sun is at its greatest distance from the celestial equator. In the Northern Hemisphere, the winter solstice occurs either December 21 or 22, when the sun shines directly over the Tropic of Capricorn. (For summer solstice, the sun shines directly over the tropic of Cancer. In the Southern Hemisphere, the winter and summer solstices are reversed.)
The winter solstice has the shortest day and the longest night of the year.
Since the sun appears at its lowest point in the sky, and its noontime elevation appears to be the same for several days before and after the solstice, people once thought it had stopped. Solstice comes from Latin solstitium, from sol, “sun” and -stitium, “a stoppage.”
For the optimists in the crowd, after this the days begin to grow longer and the nights shorter.