November 3rd is Culture Day in Japan.
Culture Day （November 3）: day for celebrating love of freedom and equality, and promoting culture.
（Commemorates the promulgation, on November 3, 1946, of the Japanese Constitution. Prior to 1945, this day was celebrated as the birthday of the Emperor Meiji.）
Culture Day has been chosen for the Day of Cartoons because the anniversary aims to promote the cultural importance of cartoons.