Choyo(重陽)is a Japanese term used to refer to one of the 5 sekku which are days marking changes in the seasons. Choyo's another name is a "Kiku no sekku(Chrysanthemum Festival)"
It is September 9th. The Japanese celebrate longevity on this day.

We pray for longevity, decorating chrysanthemums and drink sake with a chrysanthemum petal on it. Since ancient times, the fragrance of chrysanthemum has been believed to have the power to purge evil spirits.