The Apostles' Fast, also called the Fast of the Holy Apostles, the Fast of Peter and Paul, or sometimes St. Peter's Fast, is a fast observed by Eastern Orthodox, Oriental Orthodox, Eastern Catholic, and Reformed Orthodox Christians. In the Byzantine tradition, the Fast begins on the second Monday after Pentecost (the day after All Saints' Sunday), whereas in the Coptic and old Syriac traditions, the Fast begins on the first Monday after Pentecost. It continues until the Feast of Saints Peter and Paul on June 29. Traditionally, its duration varies from eight to forty-two days because of the moveable nature of Pascha. However, in Eastern Orthodox Churches that follow the Revised Julian calendar, the fast can be as long as 29 days, or may not occur at all in some years.