December 13, 1545Council of Trent begins.
The Council of Trent was the 16th-century Ecumenical Council of the Roman Catholic Church. It is considered to be one of the Church's most important councils. It convened in Trent (then capital of the Prince-Bishopric of Trent of the Holy Roman Empire, now in modern Italy) between December 13, 1545, and December 4, 1563 in twenty-five sessions for three periods. Council fathers met for the first through eighth sessions in Trent (1545–7), and for the ninth through eleventh sessions in Bologna (1547) during the pontificate of Pope Paul III. Under Pope Julius III, the council met in Trent (1551–52) for the twelfth through sixteenth sessions. Under Pope Pius IV, the seventeenth through twenty-fifth sessions took place in Trent (1559–63).