Bodhi Day is the Buddhist holiday that commemorates the day that the historical Buddha, Siddhartha Gautama (Shakyamuni), experienced enlightenment, also known as bodhi in Sanskrit and Pali. According to tradition, Siddhartha had recently forsaken years of extreme ascetic practices and resolved to sit under a peepal tree and simply meditate until he found the root of suffering, and how to liberate oneself from it.
Bodhi Day is observed in many mainstream Mahayana traditions including the traditional Zen and Pureland Buddhist schools of China, Korea, Japan, and Vietnam. In Japanese Zen, it is also known as Rohatsu. In Tendai and other Japanese sects, it is called either Shaka-Jōdō-e (釈迦成道会) or simply Jōdō-e (成道会).