Each year on April 8th, Japan celebrates Buddha’s Birthday, Hana Matsuri (花祭り - The Flower Festival). According to Buddhist tradition, Prince Siddhartha Gautama (Sakyamuni Buddha), the son of King Suddohana and Queen Maya, was born on 8 April 566 B.C. in the garden of Lumbini, in Nepal. On this day, in Buddhist temples, an interesting ceremony called Kanbutsu-e (潅仏会 - The Bathing of Buddha) takes place. Originating from China, Kanbutsu-e was first attested in Japan in the year 606, in Nara. On a flower decorated altar (hana mido), symbolizing the Lumbini garden, a small statue of Buddha, Tanjoubutsu (Buddha’s Birth), is placed in a shallow metal bowl.

It's a festival. http://en.wikipedia.org/wiki/Buddha%27s_Birthday