The Feast of Saint Michael and All Angels, or Michaelmas, takes place on 29 September each year. It is a Christian celebration of the angels, but in particular is acknowledges Michael—the greatest of the archangels—who supposedly defeated Lucifer during the war in heaven. It was believed that the day marked Satan’s fall to earth, where he landed in a blackberry bush and cursed the fruit, so Michaelmas is the last day blackberries can be picked.
During the Middle Ages Michaelmas was a Holy Day of Obligation, meaning parishioners were expected to cease from working for the day and attend mass at their local church. It was one of four Quarter Days, along with Lady Day, Midsummer, and Christmas, where debts from the previous quarter would be settled, and it also marked the beginning and end of the year for husbandry. Hiring fairs would take place, local representatives would be elected including the Mayor of London, and in Ireland rent would be due as Michaelmas was a Gale Day. The day would be marked with processions to mass, and it was traditional to name a boy born on Michaelmas Michael.
The peasants will tell their children, after Michaelmas Day, not to eat the Grian-mhuine (Blackberries); and they attribute the decay in them, which about that time commences, to the operation of the Phooka, a mischievous goblin, sometimes assuming the form of a bat or bird, and at other times appearing as a horse or goat.Richard Folkard, Plant Lore, Legends, and Lyrics
The link between Michaelmas and blackberries applies more to the old Julian calendar date, rather than the contemporary Gregorian date. Then it would have fell on what is now 11 October, when any blackberries not yet picked would be approaching rotting. The Devil’s curse upon them is sometimes attributed to him scorching berries with his breath, stamping upon them, or either he or his minions spitting or urinating upon blackberry bushes following his fall from heaven. The weather was an important factor, as if there were clear skies on Michaelmas it was believed that a long winter was ahead. On Michaelmas it was traditional to eat and share goose, known as the stubble-goose or rucklety goose, as legend tells of a son of an Irish king who choked on goose meat and was resurrected by Saint Patrick on Michaelmas. The king then declared goose be sacrificed in honour of the angel Michael each year and distributed amongst the poor. A grain cake made from barley, oats, and rye known as the Michaelmas Bannock was also prepared and baked without using any metal implements, and donated to the poor in memory of friends who had died in the past year.
Today Michaelmas is noted in some circles, including the legal profession in the United Kingdom where it still marks one of the year’s quarters. Many other celebrations have died out, though the legend of Lucifer and the blackberries remains popular.