Answer:
Catholicism started fifty days after the first Easter, which was the day following Passover (early spring) in the year (approximately) 33 A.D., in other words, fifty-three days after Jesus' death on the cross when He sent the Holy Spirit down on the early church. That day is called Pentecost, which is the "birthday of the Church" and is celebrated each year fifty days after Easter. This year (2010) it will be the 23rd of May