January 1, the solemnity of Mary, Mother of God
Thursday of the Sixth Week of Easter, the solemnity of the Ascension
August 15, the solemnity of the Assumption of the Blessed Virgin Mary
November 1, the solemnity of All Saints
December 8, the solemnity of the Immaculate Conception
December 25, the solemnity of the Nativity of Our Lord Jesus Christ
Advent - four weeks of preparation before the celebration of Jesus' birth. Advent begins on a Sunday and includes three other Sundays leading up to Christmas. The first Sunday is the one closest to the Feast of St Andrew the Apostle on November 30th, whether before or after.
Christmas - recalling the Nativity of Jesus Christ and his manifestation to the peoples of the world.
Christmas Octave: December 25-January 1.
12 days of Christmas: Christmas Octave + 4 days to Epiphany.
Lent - a six-week period of penance before Easter.
Sacred Paschal Triduum - the holiest "Three Days" of the Church's year, where the Christian people recall the suffering, death, and resurrection of Jesus (from the evening of Holy Thursday to the evening of Easter Sunday).
Easter - 50 days of joyful celebration of the Lord's resurrection from the dead and his sending forth of the Holy Spirit.
Holy Week = from Palm Sunday to Easter Sunday.
Ordinary Time - divided into two sections (one span of 4-8 weeks after Christmas Time and another lasting about six months after Easter Time), wherein the faithful consider the fullness of Jesus' teachings and works among his people.
Epiphany = a season for adoring the glory of Christ
Christmas = to commemorate Christ's grace
Lent = to commemorate his temptation
Good Friday = to commemorate his sufferings and death
Easter Day = to commemorate his victory
Ascension Thursday = to commemorate his return to the Father
Advent = the anticipation of his second coming