December 21 is the Feast Day of Boo-Hollie, which is celebrated among small farming communities in the Highlands. While the exact observance varies wildly from area to area, it frequently involved red ribbons, cow-shaped cookies, and bonfires; and was always observed five days before Dies Natalis Solis Invicti on the old calendar; which is now four days before, owing to the switching around of dates when calendars were reformed in the 1300s.
Boo-Hollie is believed to keep the cows safe for a year, and some scholars believe that in ancient times it involved leaving a live cow on a fairy mound as a tithe to the ancient powers of the earth, so that the rest of the herd would be left safe for the coming year.