Kanbutsu-e, Hana Matsuri and Amacha

In Japan, Buddha's birth is also celebrated according to the Buddhist calendar but is not a national holiday.

On this day, all temples hold Kanbutsu-e (Japanese: 灌仏会), 降誕会 (Gōtan-e), 仏生会 (Busshō-e), 浴仏会 (Yokubutsu-e), 龍華会 (Ryūge-e), 花会式 (Hana-eshiki) or 花祭(Hana-matsuri, meaning 'Flower Festival').

The first event was held at Asuka-dera in 606. Japanese people pour ama-cha (a beverage prepared from a variety of hydrangea) on small Buddha statues decorated with flowers, as if bathing a newborn baby.
 
Amacha (甘茶, literally 甘いamai=sweet and 茶 cha=tea, also transcribed as あまちゃ) is a Japanese herbal tea made from fermented leaves of Hydrangea macrophylla var. thunbergii.

Amacha means sweet tea.

This tea contains tannin and phyllodulcin, a sweetener 400-800 times sweeter than table sugar (sucrose)^[1] or 2 times sweeter than saccharin. It does not contain caffeine.

The beverage is credited with antiallergic properties. It is also used in the prevention of periodontitis.

This tea is often used in ceremonies celebrating Buddha's Birthday, in Japanese Buddhism on April 8. At that occasion, Japanese people pour amacha on small Buddha statues decorated with flowers, as if bathing a newborn baby.

Buddha's Birthday is the birthday of the Prince Siddhartha Gautama.