Established during the Meiji-period as a National Holiday, Shunbun No Hi is a holiday deeply rooted in Shinto beliefs and Buddhism. It is a day that occurs on the date of the Northward equinox in Japan Standard time (due to the need of recent astronomical measurements) and the date of the Holiday is usually declared in February the previous year (usually celebrated on the 20th or 21st of March).
It is the day when day and night are of equal length when the Japanese believe is the best time to commune with nature and show their love for all living things.
It is associated with the Buddhist Higan practices. Higan is a term that loosely means “Other Shore”. Buddhists believe that the worldly life is symbolically divided from the world of Enlightenment by a river filled with sorrow and pain. Those that manage to pass to the Other Side can be free from the worldly attachments and enter Nirvana. Nirvana is a transcendent state where there is no suffering, desire and so forth and a person is released from the effects of karma and the cycle of rebirth and death. Nirvana is the final goal of Buddhism.
Higan is popular on Shunbun No Hi because of the belief that when day and night are on equal length the Lord Buddha will appear to help souls make the crossing to the Other Shore.
Higan itself was observed in Japan in the 8th century.
On Shunbun No Hi the Japanese usually visit the graves of ancestors and loved ones, cleaning the tombstones and offering incense and flowers. It is considered to be a joyful event; because Shunbun No Hi is also the time that the winters chill leaves and the promise of the cherry blossoms in bloom are near…
Here is more interesting information on Shunbun No Hi: http://goo.gl/NOctTy
And here is an article on food usually eaten on Shunbin No Hi: http://goo.gl/MhKT5N