What Is "Goku Day"? Goku Day is an official anniversary certified and registered by the Japanese Anniversary Association. Why May 9th? Well, since in Japan the date is written in the order 5/9, and because 5 and 9 can be read as "Go" and "Ku", the numbers combine to make Goku's Japanese kanji! Thus, May 9th became Goku Day! This site has also been powered up to commemorate Goku Day! It's now equipped to bring the latest Dragon Ball info to fans all around the word in 5 languages: Japanese, English, French, German, and Spanish!