Alexander V
Traditionally, the Catholic Church considered Gregory XII's papacy to have ended in 1409 with the election of Alexander V. In 1958, Pope John XXIII selected the regnal number XXIII, citing "twenty-two [sic] Johns of indisputable legitimacy." Since the previous John XXIII (1410–1415) had succeeded Alexander V, the Pisan line became illegitimate. Gregory XII's papacy was extended to 1415, and Alexander V is now regarded by the Catholic Church as an antipope. Alexander V remains in the numbering sequence, since Rodrigo Borgia had already taken the name Alexander VI in 1492.