Setsubun, which literally means “dividing season,” marks the day before a new season starts according to the traditional East Asian lunisolar calendar. While there is a setsubun for each season, the one we typically refer to is the Spring Setsubun. According to the Japanese calendar, Spring Setsubun in 2017 falls on February 3rd; however, on rare occasions, it can fall on February 2nd.
During Setsubun, people engage in the custom of mamemaki(please see the mamemaki post for details). People also eat an entire roll of sushi, that is called Ehōmakifor a good luck. It’s not good to slice the roll because the luck will be cut off as well.