A religious service is performed for four previous emperors (going back four generations from the current emperor) on the anniversary of their death each year, while a religious service is performed for other emperors only on Shiki nen sai: 3 years, 5 years, 10 years, 20 years, 30 years, 40 years, 50 years, subsequently 100 years after the death of an emperor.
歴代天皇の祭祀は、先帝四代(現天皇の前4代の天皇)は毎年崩御日に祭祀されるが、それ以外の天皇は式年祭（3年・5年・10年・20年・30年・40年・50年・以後100年ごと）にのみ祭祀が行なわれる。