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Spriing equinox (春分の日 shunbun no hi) is a national holiday that is the celebration of spring and love of nature. 

There is another side to this.  This day is also known as 彼岸の中日 higan no chunichi. Along with obon in the summer, the two equinoxes are the time when familes visit the family grave, wash the tombstone, and offering flowers.  During this time, the weather becomes warmer, so there is a saying in Japan - 暑さ寒さも彼岸まで atsusa samusa mo Higan made (Heat and cold lasts until Higan).