February 11th is cerebrated as National Foundation Day.
It is a National Holiday in Japan.
Based on Nihon-shoki (the oldest chronicles of Japan), the first Emperor of Japan, Jinmu（神武）, ascended to the throne on this day. In Japanese, 神（Jin）means God and 武（Mu）means martial arts. It is said that the present Imperial family are the descendants of the first Emperor Jinmu, which means Japan has had the longest lineage in the world for some 2,678 years.
It had been cerebrated as Empire Day called “Kigen-setsu” until the end of World War II. It once discontinued after the war due to political purposes. In 1966, however, it was designated as a national holiday again under the name of National Foundation Day.
As Nihon-shoki includes the legendary episodes, it is said the date is not actually defined. So this day is designated as the day ”to reflect on the establishment of the nation and to nourish a love for the country”. In some ways, it might be a bit different from the Independent day or Liberation Day of other countries.
How people celebrate ?
Some shrines held memorial ceremonies. The representative one is at Meiji-jingu shrine in Tokyo and you might see the ceremonial procession including marching bands, portable shrines called “Mikoshi” and people waving the Japanese flags around Omotesando area on Feb. 11th.