After eight years as the Roman Catholic archbishop of Philadelphia, Charles J. Chaput turns 75 this week, a milestone that will mark the beginning of the end for his tenure leading the ninth-largest diocese in the United States.

Under church law, prelates must offer to resign upon reaching that birthday, which comes Thursday for Chaput. It is up to Pope Francis to decide whether to accept it, reject it, or to keep the archbishop on until a successor can be named. Church officials have said little about Chaput’s future. But he has made his intentions clear.