The winter solstice will occur on Friday 21st December this year. This is when the sun reaches it's most southerly declination of -23.5°. (In other words when the North pole is tilted at 23.5° away from the sun). This is the point in the Northern hemisphere where there will be the least amount of daylight this year. Good news is that it gradually gets lighter from here on in. (21/12/12 that is.)
Diagram for illiterates...
Diagram for illiterates...