noun
imperial memorial ceremony held on fixed anniversaries
A formal ceremony conducted at the Imperial Palace on specific anniversaries (e.g., 3rd, 5th, 10th, 20th, 30th, 40th, 50th, 100th) of an emperor's or empress's death. The term is primarily used in historical and official contexts.
See also: 式年
明治天皇の式年祭が皇居で執り行われた。
The imperial memorial ceremony for Emperor Meiji was held at the Imperial Palace.
Refers to the fixed years or anniversary cycle itself, while 式年祭 is the ceremony held on those years.
Compound of 式年 (shikinen, 'fixed years') and 祭 (sai, 'ceremony, festival'). The exact historical derivation is uncertain, but the term is conventionally associated with imperial memorial rites.