The third anniversary Mitamamatsuri corresponds to Buddhist's third anniversary memorial service, but note that in Buddhism, the year of death is counted as the year one, thus the third anniversary being held in two years after death, whereas the third anniversary Mitamamatsuri is held in three years after death (same for the fifth and 10th anniversary Mitamamatsuri).
三年祭は仏式でいうなら三回忌に当たるものなのだが、仏式の三回忌は死んだときを一回目と数えて一周忌の翌年に行われるのだが三年祭は実際に死んだ年から三年目（以下五年祭・十年祭とも同様）となるため、注意が必要である。