The Annunciation, on 25 March, celebrates the angel Gabriel's announcement to Mary that she would bear the Christ, and her consent, recounted in Luke's Gospel. Its date is not arbitrary: it stands exactly nine months before Christmas, and in the older reckoning it was linked to the belief that Christ was conceived and died on the same date, so that 25 March was held to be both the conception and the crucifixion. On this "calculation" some historians locate the very origin of the 25 December nativity.
In England 25 March, Lady Day, was long the start of the civil and legal year and one of the quarter days for rents and contracts, until the calendar reform of 1752 moved new year to 1 January. Theologically the feast marks the Incarnation itself, the moment the Word is held to have become flesh, and its liturgy accordingly ranks high in both East and West; where it falls within Holy Week or Eastertide, elaborate rules govern its transfer. The scene, the angel, the lily, the startled and assenting Virgin, is one of the most painted subjects in Western art, and Mary's "let it be to me according to your word" is read as the pattern of faithful consent.