The Christian festival of Pentecost
It was the most significant day for the Knights of Christianity and the Realms they guarded and protected.
They followed the practice to do no ordinary work, and to offer the first fruits of Spring to the Christ - their Lord, that Spirit they choose to follow and obey that was to appear before them, or to give a sign as often happened, as they gathered together waiting for the sign on the day of Pentecost. This feast is 2 days: Pentecost Sunday, and Monday.
Numbers 28:26 “At the Festival of Harvest, when you present the first of your new grain to the Lord, you must call an official day for holy assembly, and you may do no ordinary work on that day."