Advent: First Sunday of Advent through December 24th.
Christmas: December 25th through The Feast of the Baptism of the Lord.
Ordinary Time: Between Christmas (The Feast of the Baptism of the Lord) and Lent (Ash Wednesday).
Lent: Ash Wednesday through Holy Saturday.
Easter: Easter Vigil through Pentecost.
Ordinary Time: After Pentecost to Advent.
The Church's Teaching on Liturgy