Happy Seven-five-three

Today, November 15th, is Shichi-go-san 7-5-3 七五三. It is a religious rite and celebration. Boys visit shrines and temples to celebrate their growth when they turn three and five years old (by the traditional Japanese age reckoning), and girls visit shrines and temples to celebrate their growth when they turn three and seven years old.

Despite it being a large celebration, practiced by the majority of families, it is not a public holiday. Morever, it doesn't have to be performed on the exact date. Most people celebrate sometime between October and November. That is why you can see children dressed in kimono or hakama at temples and shrines at this time of year. 

The most likely theory about its origin is that it began on November 15th (lunar calendar) in 1681, as a prayer for the health of Tokugawa Tokumatsu. Additionally, November in the lunar calendar is the month to give thanks to the gods for the harvest, and the 15th day of the lunar calendar is "the day when demons do not roam" and "a day when it is auspicious to do anything," so November 15th became the registered date.