The Paschal cycle, in Eastern Orthodox Christianity, is the cycle of the moveable feasts built around Pascha (Easter).[a] The cycle consists of approximately ten weeks before and seven weeks after Pascha. The ten weeks before Pascha are known as the period of the Triodion (referring to the liturgical book that contains the services for this liturgical season). This period includes the three weeks preceding Great Lent (the "pre-Lenten period"), the forty days of Lent, and Holy Week. The 50 days following Pascha are called the Pentecostarion (also named after the liturgical book).
The Sunday of each week has a special commemoration, named for the Gospel reading assigned to that day. Certain other weekdays have special commemorations of their own. The entire cycle revolves around Pascha. The weeks before Pascha end on Sunday (i.e., the Week of the Prodigal Son begins on the Monday that follows the Publican and the Pharisee). This is because everything in the Lenten period is anticipatory of Pascha. Starting on Pascha, the weeks again begin on Sunday (i.e., Thomas Week begins on the Sunday of St. Thomas).
While the Pentecostarion closes after All Saints Sunday, the Paschal cycle continues throughout the entire year, until the beginning of the next Pre-Lenten period. The Tone of the Week, the Epistle and Gospel readings at the Divine Liturgy, and the 11 Matins Gospels with their accompanying hymns are dependent on it.