Historical Events in Church Annals for August 12:
Death of Pope Sixtus IV, 212th successor of Peter. It was Sixtus who constructed the Sistine Chapel which was later decorated by Michelangelo. He was an expert politician and a generous patron of the arts. He celebrated the 7th Jubilee in 1475 and prolonged it to Easter of 1476 as well as instituting the Feast of Saint Joseph on March 19th.
The Spanish explorer Ponce de Leon along with a cadre of Franciscans and Dominicans lands in Puerto Rico, bringing the faith to that island where it has flourished ever since.
Pope Pius XII issues his famous encyclical Humani generis which dealt with false opinions threatening to undermine the foundations of Catholic doctrine.