At about noon today, the North Pole will be tilted furtherest from the sun. It's called the winter solstice, and it not only makes Santa's trip a little more difficult, it's also when the sun appears at its lowest altitude above the horizon.
Broken down: It's the shortest day of the year.
As this calculator on sunrise and sunset shows, daylight in eastern Pennsylvania today shrinks to nine hours, 16 minutes and two seconds.
Sunrise is at 7:22 a.m. and sunset at 4:38 p.m.
Good news, tomorrow, we will have about 2 seconds more daylight than today. And that trend will continue until the summer solstice, only six months away.