Considered a feast of the Lord, the solemnity carries the following titles in ancient Roman liturgical books: Adnuntiatio Domini, Adnuntiatio Dominica or Dominicae Incarnationis, Conceptio Domini Nostri Iesu Christi (secundum carnem); Conceptio Sanctae Mariae de Spiritu Sancto. However, the current office and Mass are predominantly Marian in character.
Counting exactly nine months before the liturgical date of Christ’s birth gives us March 25. But in the ancient Churches, the mystery of the Incarnation was celebrated shortly before Christmas (for example, in the East, Milan, and Ravenna). In Spain, the Tenth Council of Toledo (in 656) prescribed moving the feast from March to December 18 due to Lent. On the other hand, the ancients considered March 25 as the day of the Lord’s death (for example, in the Martyrologium Hieronymianum).
Saint Augustine is the first to speak of this day as the day of the Savior’s conception in the womb of the Virgin Mary. The oldest original sources of the solemnity date back to the 6th century (Abraham of Ephesus). A Western author from the 11th century (Pseudo-Cyprian, De Pascha Computus) believed that Jesus Christ was incarnated on the spring equinox, that is, on this very day, which was also believed to be the day the first Adam was created.
