Winter solstice: things you should know about the shortest day of the year
What is the winter solstice, and why do we have it?
"Earth's axis is tilted 23.5 degrees relative to its orbit, and on December 21, Earth will be at the point in its orbit when the North Pole is tilted at its maximum away from the sun," Schneider told CBS News. "The effect of this in the Arctic is completely in darkness as Earth spins that day."
For those of us in the Northern Hemisphere, it's the day with the shortest amount of daylight — less than 12 hours — and our longest night of the year. However, that's not the case for everyone. While it's winter for those of us in the Northern Hemisphere, people in the Southern Hemisphere experience it as their summer solstice with the longest stretch of daylight.
When does the winter solstice occur?
The Earth's North Pole will be tilted farthest from the sun at 11:27 am ET on Thursday, Dec. 21, 2017, according to the National Weather Service.
Why isn't the winter solstice on the same day each year?
The date of the winter solstice varies from year to year for people in different time zones. It typically occurs around Dec. 21 or 22, though on rare occasions it can be as early as Dec. 20 or as late as Dec. 23, according to the Weather Channel.
That's because our calendars aren't a precise match to the solar year.
Schneider writes: "Earth takes about 365 1/4 days to orbit the Sun. Next year, the moment of the solstice will be about 6 hours later at 5:23 pm ET. In 2019, it will be at 11:19 pm ET, so for people living in Puerto Rico and other time zones to the east, the date of the solstice will be on the 22nd."