Have you heard to Shichi-Go-San in Japan? It literally means Seven-Five-Three in English and this is a festival for 7 years old girls and 5 years old boys, and sometimes 3 years old children. It is held on November 15th every year to celebrate well growth of young children. On this day, you will see a lot of children wearing Japanese traditional clothes and lining up with their parents in front of shrines.
I think this applies to most of countries, but a lot of children died due to lack of medical system in the past. They somehow believed odd numbers are lucky and the practice of celebrating the survival of children has started. The five-year-old boys wear hakama for the first time and seven-year-old girls wear kimono. After dressing up, they visit shrine to protect themselves from evil spirits and wish for a long life.
