While it may be common knowledge that the winter solstice is the shortest day(light) of the year in the northern hemisphere, there are some other details that are less commonly mentioned.
All of the darkness we are experiencing is due to the fact that the sun is shining farthest to the south, directly over the Tropic of Capricorn. This phenomena actually occurs at a specific time, rather than for an entire day, and that time differs from year to year. This year it occurs at 4:49 UTC on December 22nd (which is 11:49pm EST on December 21st!).
Another lesser known fact is that this is NOT the date of the earliest sunset and latest sunrise! The earliest sunset actually happens earlier in December and the latest sunrise doesn’t occur until early January.