Tsukinami-no-matsuri (literally, monthly festival) is a festival in shinto. In Ise-jingu Shrine, tsukinami-no-matsuri held in June and December and Kanname-no-matsuri (Kanname-sai festival) are called sansetsu-sai festival or sanji-sai festival.
In the old days, tsukinami-no-matsuri seemed to be held monthly, however, it was determined in the "Engishiki" (an ancient book for codes and procedures on national rites and prayers) to hold tsukinami-no-matsuri on 11th day of June and December. Tsukinami-no-matsuri is held in the Imperial Court and Ise-jingu Shrine and, on the morning of 11th day, heihaku (silk as a gift) was provided from the Imperial Court to 304 gods worshipped in Kinai area (hanhei). Later on, Ise-jingu Shrine only conducted hanhei and, when the Muromachi period started, hanhei was abolished due to Onin War, etc., however, hanhei was revived in the Meiji period. Currently, many shrines throughout Japan determine a specific day of the month and conduct tsukinami-no-matsuri on that day.