Japanese National Foundation Day

February 11 is National Foundation Day, a national holiday for Japanese people to remind themselves of the nation's founding and foster their love for the nation.
Japan switched from the traditional Japanese calendar - a lunar calendar based on the waxing and waning of the moon - to the Gregorian calendar starting in January 1873. It was at this time that the day of the enthronement of Emperor Jinmu, the first Japanese emperor, was made a national holiday and named Kigen-setsu. February 11 was determined as the day of enthronement by calculating the date in the solar calendar corresponding to the date recorded in the Nihon Shoki (The Chronicles of Japan), Japan's first history compiled on imperial orders. (However, many historians believe that Emperor Jinmu's enthronement, as described in the Nihon Shoki, was not a historical fact but folklore.)

Before World War II government offices and schools throughout Japan held all sorts of celebrations on Kigen-setsu, but after the war, the holiday was abolished for various reasons. Still, many voices lamented its passing, so that in 1966 the day was again made a national holiday as National Foundation Day.
History
Though celebration of the story of the foundation of Japan by Emperor Jimmu stretches back into Japanese history, National Foundation Day did not become an official holiday until January 1873, when Japan switched from its lunisolar calendar to the Gregorian calendar. Japanese scholars used the Nihonshoki (日本書紀), to derive the exact date, February 11, 660 BC. However, it should be noted that historians have yet to find evidence of either the significance of this date or even the existence of Emperor Jimmu outside of the Nihonshoki.
In its original incarnation, the holiday was named Kigensetsu (紀元節, trans: Empire Day). It is thought that the Meiji Emperor may have established this holiday to bolster the legitimacy of the imperial family following the abolition of the Tokugawa Shogunate. Publicly linking his rule with the mythical first emperor, Jimmu, and thus Amaterasu, the Meiji Emperor declared himself the one, true ruler of Japan.
With large parades and festivals, in its time, Kigensetsu was considered one of the four major holidays of Japan.Given its reliance on Shinto mythology and its reinforcement of the Japanese nobility, Kigensetsu was abolished following World War II. It was re-established as National Foundation Day in 1966. Though stripped of most of its overt references to the Emperor, National Foundation Day is still a day for expressing patriotism and love of the nation.