Does anyone know the origin of folk cooking black glutinous rice on the eighth day of April?

According to legend, during the Warring States Period, Sun Bin, the descendant of soldier Sun Wu, went into the mountains with Pang Juan, the general of Wei State, and learned the art of war from Guiguzi. Guiguzi taught the essence of Sun Tzu's Art of War to the modest and studious Sun Bin. Pang Juan, jealous of talent, framed Sun Bin, cut off his tibia, locked Sun Bin in the stable, and forced him to hand over Sun Tzu's Art of War by starvation.

The kind jailer was very sympathetic to Sun Bin's misfortune. He fooled Pang Juan's men, used local materials, mashed glutinous rice with ebony leaves, cooked it, kneaded it into small dumplings, and secretly gave it to Sun Bin. Because its shape and color are similar to horse manure, Pang Juan never found the secret. Later, Sun Bin got revenge after being rescued.

According to legend, Sun Bin ate black rice for the first time in Xiaoman on the eighth day of the fourth lunar month. The local people followed this custom for generations and cooked black rice on this day to commemorate this strategist. Because the eighth day of the fourth lunar month happens to be the birthday of Buddha Sakyamuni, black rice has a homophonic nickname "Amimi".