Via WSJ:

ROME—Pope Benedict XVI said on Monday that he plans to step down at the end of this month because of his deteriorating physical strength, a move that hasn’t happened in the Roman Catholic Church in centuries and that is likely to pave the way for a new pontiff by Easter.

“After having repeatedly examined my conscience before God, 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,” the 85-year-old pope said in a declaration in Latin to a gathering of cardinals on Monday.

The pope added that his strength in the last few months had “deteriorated in me to the extent that I have had to recognize my incapacity to adequately fulfill the ministry entrusted to me.”

In the declaration, the pope—who has been in office since April 2005—said he was “well aware of the seriousness of this act,” and added that he was renouncing his ministry “in full freedom.”

The resignation due to take effect at 8 p.m. GMT on February 28, Greg Burke, the Vatican’s media adviser, said.

Normally, after a pope dies, there is a nine-day mourning period before the start of the selection of a new pope. However, this time the conclave’s process to choose the next pontiff can begin right away, Mr. Burke said. “This means we’ll have a new pope by Easter,” he added.

“The act of renouncing is a very rare occurrence,” said Dario Morelli, a canon law Ph.D student working at Portolano Cavallo legal studio.