Oyasama Birth Celebration Service
The Oyasama Birth Celebration Service (Oyasama go-tanjosai おやさま御誕生祭) held at Tenrikyo Church Headquarters in Jiba on April 18 every year, commemorates the birth of Oyasama on the lunar calendar date of 4/18/1798. The Birth Celebration Service, which is treated as a Grand Service, begins at 10:00 a.m. Unlike the Spring Grand Service and the Autumn Grand Service, the Oyasama Birth Celebration Service is only observed at Church Headquarters.
In his service prayer at the inaugural Oyasama Birth Celebration Service in 1934, the second Shinbashira Shozen Nakayama said, “We absolutely have no words to convey our apologies for our carelessness that allowed a ceremony to celebrate Your birth to be neglected until today.”
Regarding why it took so long before Oyasama’s birth came to be annually celebrated in Tenrikyo, Hinagata kiko explains:
- “One of the reasons why Oyasama’s birthday was not celebrated stemmed from the reality that there was no such custom in Japan. This was the case until after the war in 1948 when the current western system (man nenrei) was put in place for the first time. The custom of celebrating birthdays every year did not exist among the general populace until then. Only a child’s first birthday or first seasonal festival (sekku) were traditionally celebrated. Traditionally, a person aged one year each New Year’s Day, making the day everyone’s birthday. One may conclude that Oyasama’s Birth Celebration Service did not exist for some time due to this custom.” 
Oyasama Birth Celebration Period
In 1935, the ten days between April 18 and 27 were established as the Oyasama Birth Celebration Period (Oyasama go-tanjo keishuku junkan おやさま御誕生慶祝旬間). The Kagura Service began to be performed each day during this period beginning in 1949.
The Women’s Association and Young Men’s Association both used to hold their respective conventions during the Oyasama Birth Celebration Period. The ten-day period also included a number of other celebratory activities, but the practice was ended after 1985. Beginning in 1986, only the Oyasama Birth Celebration Service has been held on April 18 as a way to emphasize the significance of the April Monthly Service on April 26.
- Tenrikyo Online: Large Number of followers Celebrate Oyasama’s 214th Birthday (2012)
- “Tenrikyo celebrates Oyasama’s 200th birthday”
- “Grand Service.” In A Glossary of Tenrikyo Terms, p. 115.
- A Historical Sketch of Tenrikyo, p. 79.
- 天理教道友社編 Tenrikyo Doyusha, ed. 『ひながた紀行』 Hinagata kiko, p. 15.
- The seasonal festival for girls was called joshi-no-sekku, celebrated on the third day of the third lunar month (now celebrated on March 3 as Girls Day). The seasonal festival for boys was called tango-no-sekku, celebrated on the fifth day of the fifth lunar month (now celebrated as Children’s Day or Boys Day on May 5). Reference note from Hinagata kiko, p. 16, n. 18.
- Hinagata kiko, p. 16.
- 『改訂 天理教辞典』 Kaitei Tenrikyo jiten, p. 154.