Today is the Feast of the Annunciation, the day when the announcement of the forthcoming birth of Jesus Christ by the Angel Gabriel is commemorated, which is traditionally nine months before Christmas, unless March 25th might fall during Holy Week, for example. Without question, the birth of Christ may be the most significant event in world history, let alone in Christian history. The Passion, Death, and Resurrection of Christ and the Day of Pentecost, when the Church was born, are days that are so essential to a Christian's understanding of who Christ is and his purpose that we would have no faith without them. However, what other significant events have helped shape Christianity (for both good and ill) over the last two millennia? Here are our top five.