The Feast and commemoration of the Apostles Peter and Paul is celebrated with the Divine Liturgy of Saint John Chrysostom which is conducted on the morning of the feast and preceded by a Matins (Orthros) service. A Great Vespers is conducted on the evening before the day of the Feast. Prior to this day, the Orthodox Church observes the Apostles' Fast, a period of fasting that begins on the Monday after the Sunday of All Saints. This Sunday is always one week after the Sunday of Pentecost, so the length of the Apostles' Fast varies from year to year depending on the date of Pascha.