Today is the winter solstice and the first day of winter in the Northern Hemisphere. It’s all due to Earth’s tilt, which ensures that the shortest day of every year falls around December 21. Some predicted that today would also mark Earth’s doomsday, thanks to a longstanding rumor that the Maya calendar ends on December 21, 2012.
Even without an apocalypse, the solstice has been an auspicious day since ancient times. Countless cultural and religious traditions mark the winter solstice; it’s no coincidence that so many holidays surround the first day of winter.
The solstices occur twice a year (around December 21 and June 21) because Earth is tilted by an average of 23.5 degrees as it orbits the sun—the same phenomenon that drives the seasons.
Being the shortest day of the year, the winter solstice is essentially the year’s darkest day, but it’s not the coldest. Because the oceans are slow to heat and cool, in December the seas still retain some warmth from summer, delaying the coldest of winter days for another month and a half. Similarly, summer doesn’t hit its heat peak until August, a month or two after the summer solstice.
Scholars aren’t exactly sure of the date of Jesus Christ’s birthday, the first Christmas.
“In the early years of the Christian church, the calendar was centered around Easter,” George Washington University’s Yeide said. “Nobody knows exactly where and when they began to think it suitable to celebrate Christ’s birth as well as the Passion cycle” — the Crucifixion and resurrection depicted in the Bible.
Eastern churches traditionally celebrate Christmas on January 6, a date known as Epiphany in the West. The winter date may have originally been chosen on the basis that Christ’s conception and Crucifixion would have fallen during the same season — and a spring conception would have resulted in a winter birth.
But Christmas soon became commingled with traditional observances of the first day of winter. Early church leaders endeavored to attract pagans to Christianity by adding Christian meaning to existing winter solstice festivals.
“This gave rise to an interesting play on words,” Yeide said. “In several languages, not just in English, people have traditionally compared the rebirth of the sun with the birth of the son of God.”
National Geographic: Winter Solstice 2012: Facts on the Shortest Day of the Year by Brian Handwork.