September 29, the feast of St. Michael and All Angels or Michaelmas fell about the time of the autumnal equinox. The equinox marked the period when the nights would be getting longer and the earth would begin to die. St. Michael came to be seen as the protector against the forces of the dark and so became very popular in the Middle Ages. Many monasteries and churches were dedicated to him, usually on high places near the sea.What are Quarter Days?
His feast was celebrated with a traditional well-fattened goose which had fed well on the stubble of the fields after the harvest. In many places, a there was also a tradition of special large loaves of bread made only for that day.
By Michaelmas the harvest had to be completed and the new cycle of farming would begin. It was a time for beginning new leases, rendering accounts and paying the annual dues. It was also one of the British and Irish quarter days.
There is also a “Michaelmas Embertide” in the Catholic discipline:
Wednesday, Friday, and Saturday after the the Feast of the Exaltation of the Holy Cross, 14 September, are known as "Michaelmas Embertide," one of 4 yearly time periods known as "Ember Days," from the Latin Quatuor Tempora, meaning "four times." They are days of fasting and partial abstinence (voluntary since the new Code of Canon Law) intended to thank God for the gifts He gives us in nature, to teach us to use them in moderation, and to help the poor. Zacharias 8:19: "Thus saith the Lord of hosts: The fast of the fourth month, and the fast of the fifth, and the fast of the seventh, and the fast of the tenth shall be to the house of Juda, joy, and gladness, and great solemnities: only love ye truth and peace."More about Ember Days.
Note that these September Ember Days must follow a full week after 14 September.
Traditional Michaelmas Goose Recipe