WELCOME TO WINTER:
(AS IF YOU DIDN'T KNOW IT ALREADY)
Last night at 00:08 am(6:08 GMT/UT) the winter solstice arrived. To see when it arrived at your location check out the Time and Date website. At that time the Sun stood directly over the Tropic of Capricorn, about 23.5 degrees south of the equator. Today is the longest night of the year for those of us here in the northern hemisphere and the longest day for those below the equator. The earliest sunset up here in the frozen north actually occurred about a week ago, and the latest sunrise won't occur until the end of December. The closest approach of the Sun to Earth(the perihelion) will occur around midnight (GMT) on January 3rd, 2008. See the Astronomy Blog for more details on the solstice and the perihelion. The winter solstice occurs each year on either the 21st or 22nd of December.
Last year the solstice occurred at 6:22(0:22 GMT) on December 21st here in Winnipeg. See the post on this blog for last December 21st, 2006 for more details on the solstice, its "exact" timing and the traditions that surround it. The choice of December 25th as 'Christmas' was formalized by Emperor Constantine so as to ease the transition to a Christian polity from the usual pagan festivities such as Saturnalia, Sol-Invictus(the undefeated Sun) and the northern customs of 'Yule'. Once more see the post from last year for more on the religious traditions of Midwinter/Christmas and the confusion between Christmas and midwinter.