January 19, 1563: The Heidelberg Catechism, soon accepted by nearly all European Reformed churches, is first published in Germany.
April 20, 1139: The Second Lateran Council, led by Pope Innocent II and attended by 1,000 church leaders, opens in Rome. The council focused on reforming the church in the wake of the East-West schism (1054) and preserving the temporal possessions of the clergy.
April 20, 1233 (some say 1232): Pope Gregory IX appoints full-time papal inquisitors and gives the Dominican order authority to carry out the Inquisition. For their vigilant and persistant work, the order won the moniker "Domini canes" or ...