Regulated by ancient traditions and recent rules, the period between popes -- known by the Latin term "interregnum" -- will begin exactly at 8 p.m. Rome time Feb. 28.
From the moment he was elected pope at the age of 78 in 2005, Pope Benedict XVI has kept a schedule that appeared light compared to that of Blessed John Paul II, but busy for a man who had wanted to retire to study, write and pray when he turned 75.
Announcing Monday that he would resign at the end of the month, Pope Benedict said, "I have come to the certainty that my strengths, due to an advanced age, are no longer suited to an adequate exercise of the Petrine ministry."
John Allen in Rome: Benedict's decision to resign has both won wide praise and raised a whole rafter of questions.
Following his resignation, Pope Benedict XVI will move to a monastery of cloistered nuns inside the Vatican, the Vatican spokesperson has stated.
Four clarifications about the pope's resignation were sent this morning by Jesuit Fr. Federico Lombardi, the Vatican spokesperson:
Pope Benedict XVI has given his resignation freely, in accordance with Canon 332 §2 of the Code of Canon Law.
Pope Benedict XVI will not take part in the Conclave for the election of his successor.
The pope's resignation is a "sign of his great care for the Church," the president of the U.S. bishops' conference, Cardinal Timothy Dolan of New York, said in a statement this morning.
"We are sad that he will be resigning but grateful for his eight years of selfless leadership as successor of St. Peter," wrote Dolan at the U.S. bishops' conference website.
Dolan's full statement, available here, follows:
Statement of Cardinal Timothy Dolan
Pope Benedict XVI's announcement that he planned to resign Feb. 28 stunned and shocked religious leaders around the world.
Analysis: Pope Benedict XVI announced Monday he will resign Feb. 28. But is that allowed? Has it happened before?
Pope Benedict XVI announced Monday that he will resign Feb. 28. "My strengths ... are no longer suited" to the papacy, he said.
A top Vatican official blamed the media for "derailing" his recent remarks on possible legal protections for unmarried couples that potentially included gay and lesbian couples.
It was the first time a rock group was the "opening act" of a plenary assembly -- usually a routine, speech-filled affair.