Why do we celebrate Christmas on Dec. 25?

SDStaff Dex replies:

History records no observation of Christmas before 354, and by that time there was no one around who remembered exactly when Jesus was born. Today, historians have all but given up trying to figure it out. They give his birth date as 6-8 BC (good trick, but this was no ordinary dude) and leave it at that.

Nobody knows exactly why Christ’s birthday is celebrated on December 25. One theory holds that this is the right date, postulating that Zachary was high priest and that the Day of Atonement fell on September 24, ergo, John the Baptist was born on June 24 and Christ dropped in exactly six months later on December 25. Modern scholars use this theory to get laughs at cocktail parties.

Another guess works backward from the supposed date of the crucifixion (March 25), figuring that Christ was conceived exactly 33 years before he died, True Believers having no use for fractional numbers. According to the most tenable hypothesis, Christ’s birthday was assigned to the winter solstice (December 25 in the Julian calendar, January 6 in the Egyptian) because the date had a ready-made pagan holiday, the “Birthday of the Invincible Sun” (or “ancient Saturnalia debauch,” as you put it).

The idea that Jesus was a Pisces probably comes from the characterization of that sign as one of spiritualism, humility, compassion, sacrifice, etc. Students of astrology will tell you it’s not kosher to work the formula backwards that way.

SDStaff Dex, Straight Dope Science Advisory Board

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