Otsukimi (お月見), also known as Tsukimi (月見) or Jugoya (十五夜), literally translates into “moon viewing” in Japanese and is a festival dedicated to enjoying the autumn moonlight. The day changes yearly as it typically falls on the 15th day of the eighth month using the traditional Japanese lunar calendar, but is usually celebrated in-between September and October. This is when the position of the moon, sun and earth is said to be at an optimal position to view the bright moon.
Otsukimi is believed to have been started by Japanese aristocrats in the Heian period before 1185 AD but also has folklore origins about rabbits and the moon. It is said that the Old Man from the Moon, disguised as a beggar, came to earth and met a monkey, a fox and a rabbit sitting around a fire. He told these animals that he was hungry and asked if they could spare some food. The monkey fetched some fruit and nuts while the fox brought back some fish. The rabbit couldn't find anything to give so instead leapt into the fire to offer himself as food. The Old Man from the Moon was overwhelmed by this sacrifice and resurrected the rabbit to live with him forever on the moon. It is said that during the full moon of Otsukimi, you can see the rabbits making mochi (glutenous rice) in the moon.
In addition to direct moon viewing, other traditions include displaying decorations made of susuki grass, reciting poetry and offering food in honor of a bountiful harvest. These food offerings include satoimo (taro root), chestnuts, edamame, dango (sweet rice dumpling) and sake.
Nowadays, in addition to enjoying special tuskimi dango, other seasonal foods are eaten while viewing the moon. As egg yolks are said to symbolize a full moon, you'll find people in Japan enjoying soba or udon noddles topped with raw egg and seaweed or special mooncake pastries filled with egg yolk.