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Richard Gadsden's avatar

Why is Christmas specifically on December 25?

Well, there are lots of midwinter festivals - just to pick Roman ones, for it was the Romans who chose the date, there is Saturnalia on 17th December, Sol Invictus on the solstice and the New Year on January 1.

But the predominant pagan midwinter festival in the second and third century, in the period when Christianity was taking off, was Sol Invictus, which was on December 25, the winter solstice. So that was the date chosen for Christmas.

Hold on... but the solstice is on the 21st, isn't it?

It is *now*, yes. The Julian Calendar was designed by the astronomer Sosigenes (of Alexandria) and implemented in (what we now call) 45 BC. In its original form, the solstices and equinoxes were on the 26th of the relevant months. Note that this was a mistake by Sosigenes - the intended solstice and equinox days were Jan 1, Apr 1, Jul 1, Oct 1, so the Kalends of Julius would be Midsummer. Ptolemy pointed out the correction in the first century AD (by which point they had drifted to the 25th) and the date of the festival of Sol Invictus was set based on Ptolemy's calculations.

By the time that the Christian calendar was being set - at the Council of Nicaea in 325AD - the Spring Equinox was now on 21 March, so the Easter calculation ("the Alexandrian computus") was set on that basis. When, in 1582, Pope Gregory, using the work of the astonomers Aloysius Lilius and Christopher Clavius, finally reformed the calendar to get rid of the drift, he dropped ten days from the calendar and this corrected the drift between 325AD and 1582AD, not all the way back to 45BC, meaning our calendar is still five days off from the actual calendar Sosigenes devised and six more from his intended calendar.

This is why we have two midwinter festivals, neither of which is on the actual date of midwinter.

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Nicholas Pretzel's avatar

I recently heard, on BBC Radio 4, that the reason for the 1914 football match was that the trenches on both sides suffered rapid flooding, forcing the soldiers to abandon them.

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