http://www.lioncity.net/buddhism/index. ... ventid=377
Its origin and significance
By Zuio H. Inagaki
Hana-matsuri means "Flower Festival". It is the popular name for the Buddha's birthday celebration, which falls on 8th April and is traditionally called bussho-e, tanjo-e, kanbutsu-e and Shakuson gotan-e.
The first hana-matsuri celebration was held in Hibiya Park, Tokyo, in 1917 by a joint group of Buddhists, headed by Ando Ryogan and Watanabe Kaikyoku. This, however, was proceded by a birthday celebration for the Buddha held in Berlin in 1901 by a group of 18 Japanese scholars who were studying there at the time, such as Sonoda Shue, Haga Yaichi, Anezaki Masaharu, Minobe Tatsukichi, Matasumoto Bunzaburo, Ikeyama Eikichi and Chikazumi Jokan. They called this celebration "Blumfest," "Flower Festival", which is the origin of Hana-matsuri.
The Term is also used for the Shinto ceremonies held in December and January in parts of Aichi Prefecture.