The start date was determined following days of deliberations and more than 100 speeches by the 115 voting cardinals who went to the Vatican to select a new pope for the world's 1.2 billion Catholics, The Washington Post reported.
Vatican officials said the cardinals, meeting in their eighth general congregation, voted to start the conclave Tuesday afternoon after a morning mass in St. Peter's Basilica.
Earlier Friday, the cardinals voted to accept the absence of the two voting-age cardinals who said they would not attend the conclave, the Post said. One, a cardinal from Jakarta, asked to be excused for health reasons.
The second is Cardinal Keith O'Brien of Scotland, who recently admitted to accusations of inappropriate sexual behavior toward priests. When he announced his resignation as leader of the Catholic Church in Scotland in February, he said he would not attend the conclave.
The announcement of a start date for the papal election provides a timetable for the vote, The New York Times reported. Holy Week begins March 24, Palm Sunday, followed by Easter Sunday on March 31.
The last day of papal duties for the 85-year-old Benedict was Feb. 28. He announced earlier he was leaving the chair of St. Peter because of health and advancing age.
Six days before his resignation took effect, the pope emeritus issued an order to the cardinals that they didn't have to wait the traditional 15 to 20 days to begin the balloting process.