It's the winter solstice today – at 1002 in Greenwich. This is the day I look forward to more and more as I get older; the day when the world begins its new year even if we humans are forced to wait for January 1st to appease the gods of market place and calendar. It's a day for remembering that we are part of Nature: New Year Day for everything but us. What a pity we cannot just fit in.
The two solstices and equinoxes are astronomically determined (not fixed exactly as they wobble around across a couple of days) and occur on/around June 21st and December 21st. Explaining Science examines all the technical stuff. The equinoxes occur in March and September, as you know.
The dates are all very close to the traditional quarter days: March 25th, June 24th, September 29th and December 25th when workers were hired and debts settled. From medieval times in England and Wales the quarter days coincide exactly with four religious festivals:
– Lady Day – the Feast of the Annunciation, March 25th
– Midsummer Day – the Feast of St. John the Baptist, June 24th
– Michaelmas – the Feast of St. Michael and All Angels, September 29th
– Christmas Day – the Feast of the Nativity, December 25th
The cross-quarter days come in between the quarter days: Candlemas (2nd February), May Day (1st May), Lammas (1st August), and All Hallows (1st November).
The obvious question is, why weren't these important feast days fixed to the astronomically significant dates? Well maybe they were before all the calendar shifting took place in 1582 (Julian to Gregorian) and before that in Julian times themselves in Rome when there was also significant reform. See this for a detailed discussion of a complicated issue.
It's all too much for me; anyway, I'm taking a rest from the world of blogs between now and Twelfth Night. It's to be hoped that this will involve more reading than scribbling; more walking than typing.
A Happier New Astronomical Year to you all.