June 29 on the Julian calendar, July 12 on the Gregorian. The Feast of Saints Peter and Paul or Solemnity of Saints Peter and Paul honors the martyrdom of the apostles Saint Peter and Saint Paul in Rome and is liturgically observed on 29 June. The celebration is of ancient Christian origin, the date selected being the anniversary of either their death or the translation of their relics. Wiki link Dates computed on the Julian calendar. Text: Wikipedia (CC BY-SA).