Complex sentence: The feast of the Annunciation is usually held on March 25; it 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.
Split into simpler sentences: The feast of the Annunciation is usually held on 25 March. It can be moved in the Catholic Church, Anglican, and Lutheran liturgical calendars., the feast is moved if necessary to prevent it from falling during Holy Week or Easter Week or on a Sunday.