The word is taken from the Latin sollemnitas, a term of uncertain origin but possibly derived from sollus (whole) and annus (year), indicating a celebration occurring at yearly intervals. The Church always celebrates each solemnity every year.
|January 1||Solemnity of Mary, Mother of God||formerly known as the Feast of the Circumcision of Christ|
|January 6||The Epiphany of the Lord||commemorates the visit of the magi; observed in most dioceses on the second Sunday after Christmas (between Jan 2 and 8) in most dioceses, including those of the United States. The Feast of the Baptism of the Lord on the next Sunday (or on Monday 8 or 9 January if the observance of this Solemnity occurs on 7 or 8 January) ends the Christmas season.|
|March 19||Saint Joseph, husband of the Blessed Virgin Mary||transferred to Monday 20 March whenever it falls on Sunday but to the Saturday before Palm Sunday if it falls on Palm Sunday or during Holy Week|
|March 25||The Annunciation of the Lord||commemorates the Archangel Gabriel's announcement to the Blessed Virgin Mary that she was to be the Mother of God; usually transferred to Monday 26 March when it falls on a Sunday but to the Monday after the Second Sunday of Easter whenever it falls on Palm Sunday, during Holy Week, or during the Octave of Easter; nowhere a holy day of obligation|
|22 March to 25 April (varies; set as the first Sunday after the first full moon after the first day of spring, the March 20/21 [vernal equinox])||Easter||commemorates the Resurrection of Christ|
|40th day of Easter (30 April to 3 June)||Ascension of the Lord||commemorates Jesus' ascension into heaven, a short time after his bodily resurrection; always falls on a Thursday; transferred to the following Sunday in some areas|
|50th day of Easter (10 May to 13 June)||Pentecost||commemorates the descent of the Holy Spirit upon the [apostles]; considered the 'birthday of the Church'; always falls on a Sunday|
|Sunday after Pentecost (17 May to 20 June)||Trinity Sunday||always on Sunday|
|Thursday after Trinity Sunday (21 May to 24 June)||Body and Blood of Christ||Corpus Christi; moved to the following Sunday (24 May to 27 June) in most areas, including the United States of America; can conflict with the Solemnity of the Nativity of Saint John the Baptist|
|Friday eight (or five) days after Corpus Christi Thursday (or Sunday) (29 May to 2 July)||Sacred Heart of Jesus||nowhere a holy day of obligation; can conflict with the Solemnity of the Nativity of Saint John the Baptist or with the Solemnity of Saints Peter and Paul, Apostles|
|June 24||The Nativity of Saint John the Baptist||nowhere a holy day of obligation; can conflict with the Solemnity of the Most Holy Body and Blood of Christ or with the Solemnity of the Most Sacred Heart of Jesus|
|June 29||Saint Peter and Saint Paul, Apostles||can conflict with the Solemnity of the Most Sacred Heart of Jesus|
|August 15||Assumption of Mary|
|November 1||All Saints|
|Last Sunday before Advent (20-26 November)||Feast of Christ the King||this is the last Sunday of the liturgical year; the first Sunday of Advent marks the beginning of the liturgical year|
|December 8||The Immaculate Conception of the Blessed Virgin Mary||transferred to Monday 9 December if 8 December falls on Sunday|
|December 25||Christmas||holy day of obligation; also known as The Nativity of the Lord|
Some solemnities are also Holy Days of Obligation, on which Catholics are required to attend Mass; some are not. Moreover, the canon law of the Catholic Church requires that on Holy Days of Obligation Catholics are to avoid "work" and "affairs" that "hinder the worship to be rendered to God" or interfere with "suitable relaxation of mind and body" just as is required on Sundays.
Solemnities of the Lord (Epiphany, Annunciation, Ascension, Corpus Christi, Trinity, Christ the King, Nativity), Solemnities of the Blessed Virgin Mary (Mother of God, Assumption, Immaculate Conception), Solemnities of Saints Listed in the General Calendar (Joseph, Nativity of John the Baptist, Peter and Paul, All Saints), All Souls Day, and proper solemnities can impede other Sundays throughout the year.
For all intents and purposes, this means that a solemnity always can impede a Sunday in Ordinary Time.