Saint Stanislaus

Stanisław was the bishop of Kraków (Poland). On April 11, 1079, he was murdered—while celebrating Mass—on the orders of King Bolesław II, who had been excommunicated by Stanisław, though the exact reason for the excommunication remains unclear.

He was canonized in 1253 and added to the Roman liturgy in 1594, with his feast day initially set on May 7. As we can see, the current calendar prefers to celebrate his memory on the day of his death.