Feast of the Annunciation
This feast is also known as the Feast of the Good News. This is the time when the Angel Gabriel brought the "Good News" to Mary, the elected one of God, that she would bear a Son. This Son was to be the the Messiah. Thus the ancient prophecy of the Messiah coming from the house of David and of a virgin was being fulfilled.
Mary agreed to cooperate with God's plan freely and without constraints. It is through Mary's acceptance, that God would rediscover His creature -- mankind -- to be able once again to have an intimate friendship (constant communion) as He did in the Garden of Eden with Adam and Eve.