The Protestant Reformation on October 31 in 1517 by Martin Luther rediscovered the true Christianity when he nailed up the 95 theses on the door of the castle in Wittenberg Germany.
The Christianity or Christian Church has been divided between the occidental Europe which is Roman Catholics and Eastern Byzantine which is Orthodoxy.
Essentially the Christian Church has been born when the apostles of Christ began to spread out the Gospel of Jesus of Nazareth after the ascension of Christ empowering by the Holy Spirit.
The Gospel of Jesus Christ that the apostle carry out was the life and work of the Christ as the Son of God making people to be repented and be saved. The first century church was also following same mission as the apostles to carry out further with Paul and others. The central message of the apostles was that Jesus as the Son of God came to this world, suffered even to death and overcome the death by the reservation. He became the Lord and Christ.