If every year we are used to the custom of eating lychee, fermented steamed sticky rice, or ash cake (cake cooked from glutinous rice with mistletoe ash) to kill insects on the Tet Doan Ngo (taking place on May 5th of the lunar calendar, or the Vietnamese Bug Killing Festival), this year, a special royal ceremony has been reenacted at the Imperial Citadel of Thang Long. It is the ritual of giving fans to the mandarins. During the Later Le Dynasty, this fan-giving ritual is simply to keep the cooling by using fans on hot summer days. This shows the king's power concern for the mandarins with the meaning of blessing, health, and peace. Professor Le Van Lan: “According to the ancient language, Spring spawns, Summer grows, Autumn recedes, and Winter hides. At that time, at (the Imperial Citadel of Thang Long) here, the yang of heaven and earth gathered here. With the southern climate, the lunar calendar is an occasion of the development cycle, the time of a person's life, and life is very important./.