On the 20th of May in the year 325, the First Council of Nicaea was officially opened which started the first ecumenical church of Christianity. The Council of Nicaea was a council of Christian bishops convened in Nicaea in Bithynia by the Roman Emperor Constantine I in AD 325. This first ecumenical council was the first effort to attain consensus in the church through an assembly representing all of Christendom, although previous councils, including the first Church council, the Council of Jerusalem, had met before to settle matters of dispute. The president of the council was Hosius of Corduba.
The main accomplishments were the the Christological issue of the nature of the Son of God and his relationship to God the Father, the creation of the first part of the Creed of Nicaea, the establishment of all round acknowledgement of the date of Easter and promulgation of early canon law.