Since the day of Setsubun falls under the day before risshun (the first day of spring) of entering spring according to the calendar, the custom was done as an annual event of yakuotoshi (ceremony to drive away evil spirits) for driving away bad luck for the year.
節分の日は暦の上で春を迎える立春の前日にあたるので、一年の災いを払うための厄落とし、年中行事として行われた。