Today is a national holiday, Day in Commemoration of the Founding of the Country (Kenkoku kinen no hi).
But wait...what is that no doing there? Why is today not just the more compact and natural "National Foundation Day" (kenkoku kinenbi)?
Funny thing about this holiday...it was promulgated in the Meiji period to honor the beginning of the rule of the Yamato line of emperors. Occupation authorities abolished the holiday. It was resurrected (after a whole lot of tries) in 1966.
The catch was (and is) that the name of the resurrected holiday acknowledges the mythological status of the official date of the founding of the nation. There can be no "National Foundation Day" per se - just a date commemorating that founding.
Hence the insertion of the no in there. A Euro-American equivalent would be to have December 25 called "Day of Christmas" rather than "Christmas Day" -- which is a far more reasonable construction, given the ahistoricity of that celebration.
One can no longer assume that Japanese governments will honor history by making this distinction between the real and the mythical. The changing of the name of today's holiday is not among the promises made in the Liberal Democratic Party's most recent manifesto. However eliminating that niggling no is surely on the reactionary movement's to-do list. With the Abe Cabinet's approval ratings now above 70% and the Chinese government doing its darndest to boster Abe's claims that Japan faces an existential crisis, few and quavering would be the voices raised in protest of the extraction of that tiny, but oh so significant, little word.