Annunciation is observed on March 25, 2018. The Annunciation, also referred to as the Annunciation to the Blessed Virgin Mary or Annunciation of the Lord, is the Christian celebration of the announcement by the angel Gabriel to the Virgin Mary that she would conceive and become the mother of Jesus, the Son of God, marking his Incarnation. Gabriel told Mary to name her son Jesus, meaning "Saviour". It is one of the twelve Great Feasts of the church year.
Many Christians observe this event with the Feast of the Annunciation on 25 March, nine full months before Christmas, the birthday of Jesus. The feast of the Annunciation is usually is moved in the Catholic Church, Anglican and Lutheran liturgical calendars when this date would fall during Holy Week or Easter Week or on a Sunday. The Eastern Orthodox Church, Oriental Orthodoxy and Eastern Catholic Churches do not move the feast, having special combined liturgies for those years when the Annunciation coincides with another feast. (With material from: Wikipedia)