In the British Isles, Michaelmas is celebrated on September 29. As the Feast of St. Michael within the Catholic church, this date is often associated with the harvest because of its proximity to the autumn equinox. Although it's not a Pagan holiday in the true sense, Michaelmas celebrations often included older aspects of Pagan harvest customs, such as the weaving of corn dolls from the last sheaves of grain.
During the medieval period, Michaelmas was considered one of the holy days of obligation, although that tradition ended in the 1700s. Customs included the preparation of a meal of goose which had been fed on the stubble of the fields following the harvest (called a stubble-goose). There was also a tradition of preparing special larger-than-usual loaves of bread, and St. Michael's bannocks, which was a special kind of oatcake.
By Michaelmas, the harvest was typically complete, and the next year's farming cycle would begin as landowners saw reeves elected from among the peasants for the following year. The reeve's job was to watch over the work and make sure everyone was doing their share, as well as collecting rents and donations of products. If a holding's rent fell short, it was up to the reeve to make it up - as you can imagine, no one really wanted to be reeve. This was also the time of year when accounts were balanced up, annual dues paid to local guilds, and new leases taken for the following year.