Kodomo no Hi is celebrated on May 05, 2018. Kodomo no Hi or Children's Day is a Japanese national holiday which takes place annually on the fifth day of the fifth month, and is part of the Golden Week. It is a day set aside to respect children's personalities and to celebrate their happiness. It was designated a national holiday by the Japanese government in 1948.
The day was originally called Tango no Sekku, and was celebrated on the 5th day of the 5th moon in the lunar calendar or Chinese calendar. After Japan's switch to the Gregorian calendar, the date was moved to May 5. Until recently, Tango no Sekku was known as Boys' Day while Girls' Day (Hinamatsuri) was celebrated on March 3. In 1948, the government decreed this day to be a national holiday to celebrate the happiness of all children and to express gratitude toward mothers. It was renamed Kodomo no Hi.
Before this day, families raise the carp-shaped koinobori flags, one for each boy (or child), display a Kintarō doll usually riding on a large carp, and the traditional Japanese military helmet, kabuto. Kintarō and the kabuto are symbols of a strong and healthy boy. Mochi rice cakes wrapped in kashiwa (oak) leaves are traditionally served on this day. (With material from: Wikipedia)