In the Orthodox Church, our worship is governed by what is called an ecclesiastical calendar. On the basis of this calendar, the worship of the particular days and seasons is delineated and defined. We don’t worship without the governorship of this calendar and wouldn’t consider doing so. Many people, who don’t understand the use of an ecclesiastical calendar think such a dependency is foolishness, some ridicule us for it, and others even pride themselves on the fact that they DON’T use an ecclesiastical calendar. In spite of this misunderstanding, we continue to use it and for several good reasons.
First, we inherited the use of a church calendar from the Apostles. We know for a fact that the first Jewish Christians continued to attend Synagogue and Temple and to celebrate the Feast Days of the Jewish calendar. The Book of Acts, for example, tells us that St. Paul was eager to return to Jerusalem to celebrate the Feast of Pentecost [Acts 20:16]. Since Pentecost was one of three major Jewish feasts, we know that Jews who celebrated Pentecost also celebrated Passover fifty days previously. The Jewish Christians did no differently.
The first Christians also celebrated the first day of the week, Sunday, as the weekly celebration of the resurrection [Acts 20:7]. This practice was based upon the fact that the resurrection of Christ took place on Sunday morning [Matt. 28:1]. In the second century, some Christians who had been trained by St. John the Apostle in the area around Ephesus insisted on celebrating a yearly festival of the resurrection; they did it on the fourteenth day of the Jewish month of Nissan, which was the calendar day of the resurrection. Others insisted on celebrating the yearly festival of the resurrection on the Sunday following 14 Nissan. Each group insisted it appealed to what it had been taught by the Apostles, who, obviously, celebrated a yearly festival of the Resurrection [and probably did so at Passover].
Although these are scant examples, and the Apostolic Church did not have the extensive calendar that we use today, the fact is that they DID celebrate according to a calendar and did so both weekly and yearly. This is one reason why we continue the practice.
The second reason for using a calendar is that it organizes our days around the telling of the story of Jesus Christ. In our calendar, we have two foci; the first is the yearly telling of the drama of salvation in Jesus Christ, the second is the daily regimen of prayer which every Christian is expected to practice.
The yearly drama is divided into seasons, and its central event is the Resurrection [Easter/Pascha]. Although there are seasons such as Advent, Nativitytide, Epiphany, Pre-Lent, Lent, Passiontide, Holy Week, Paschaltide, Pentecost and what is sometimes called "Ordinary Time," they each depend upon the event of the Resurrection of Christ. However, each season has a particular portion of the drama of salvation to emphasize. For example, Nativitytide tells us of the birth of our Lord Jesus Christ, and Christmas is a day in that season. Epiphany speaks of the Three Kings and the Baptism of our Lord, Holy Week retells our Lord’s journey into Jerusalem and his Passion, Pentecost tells about the giving of the Holy Spirit to the Church which believed in Jesus’ resurrection. Each points to Pascha and most depend upon the dating of Easter for their own dates.
On a yearly basis, we hear each of these particular aspects of the drama of salvation. Weekly, as we follow the Apostolic practice, we tell the same story and events in our Sunday liturgy. Indeed, the Sunday mass looks like mini version of the calendar year; Advent is represented in the Kyrie Eleison, Nativity in the Gloria In Excelsis, Holy Week and Good Friday in the Offertory of the Mass, Pascha [Easter] at the end of the Canon of the Mass ["Behold the Lamb of God"]. Thus, Sunday reflects the yearly event.
The other aspect of the calendar is the daily regimen of prayer. Each day of the calendar is either devoted to an event of the yearly cycle [such as the Presentation of Christ in the Temple or the Annunciation to the Blessed Virgin Mary] or to an individual event, usually the life of a particular saint. In the case of the commemoration of saints, each day has its celebration of a particular saint’s life, replete with biography, Scripture and patristic readings [sermons from ancient Christians], and particular prayers, psalms and hymns. In addition, each day has an assignment for the Mass, as daily prayer and the Mass go hand in hand.
This may seem to some to be much ado about nothing, but we believe that one cannot practice the Christian Faith without operating on some sort of calendar, be it an ecclesiastical calendar or a secular calendar. If one worships on Sunday, and commemorates Christmas and Easter, he has an ecclesiastical calendar, albeit a simplified one. If one claims that he abides by no calendar at all, yet meets on a pre-determined day each week, he is abiding by the secular calendar, and, thus, his Christian life IS governed by a calendar. If one uses an extensive ecclesiastical calendar, he is relying on ancient Christian practice to shape and inform his daily and yearly prayer and worship, and the end is the arrangement of all of one’s days around the story of Jesus Christ.