Second Vatican Council
The Second Ecumenical Council of the Vatican, commonly known as the or , addressed relations between the Catholic Church and the modern world. The council, through the Holy See, was formally opened under the pontificate of Pope John XXIII on 11 October 1962 and was closed under Pope Paul VI on the Solemnity of the Immaculate Conception on 8 December 1965.
Catholic Church and ecumenism
The Catholic Church recognizes 21 Ecumenical or General Councils: Nicaea I (325), Constantinople I (381), Ephesus (431), Chalcedon (451), Constantinople II (553), Constantinople III (680–681), Nicaea II (787), Constantinople IV (869–870), Lateran I (1123), Lateran II (1139), Lateran III (1179), Lateran IV (1215), Lyons I (1245), Lyons II (1274), Vienne (1311–1312), Constance (1414–1418), Florence (1438–1445), Lateran V (1512–1517), Trent (1545–1563), Vatican I (1869–1870), Vatican II (1962–1965).