The Nativity Fast is a period of abstinence and penance practiced by the Eastern Orthodox, Oriental Orthodox, and Eastern Catholic Churches, in preparation for the Nativity of Christ, (December 25). Like the Western Advent, the Nativity fast prepares Eastern Christians for the celebration of Christmas. However, it differs in two significant respects: The Eastern fast runs for 40 days instead of four (Roman rite) or six weeks (Ambrosian rite) and thematically focuses on proclamation and glorification of the Incarnation of God, whereas the Western Advent focuses on the two comings (or advents) of Jesus Christ: his birth and his Second Coming or Parousia.