For those who don't know what Cirno Day is:
Cirno Day is the day OUR GLORIOUS ICE FAIRY CHIRUNO is honored. Why the "9" and the "⑨" you might wonder? The answer is easy, because of a manual screenshot where Cirno is next to a ⑨-ball, since then 9/9 is offically Cirno Day also known as "The Strongest Day"
|Low quality picture of the manual screenshot|
As a tribute to CHIRUN⑨ some movies I found on Youtube.