Pope Celestine V abdicated on this Day in 1294.
Normally, Popes only give up the triple crown when it's pried from their cold, dead hands; but every few centuries one gives it up voluntarily.
After the death of Nicholas IV in 1292, the Cardinals, evenly split between Orsini and Colonna factions, struggled to agree on a successor. They debated and voted off and on for two years. The papal interregnum (sede vacante) greatly disrupted the governance of Rome, not least of all because prisoners were traditionally released during this time. This lead to a great improvement in both the quantity and quality of Roman street fighting, but was generally bad for pretty much everything else.
The lack of a Pope was creating such trouble that even a mountain-top hermit noticed it. That hermit, named Pietro da Morrone, wrote a letter to the Cardinals telling them that God would punish them if they didn't quickly elect a new Pope. In the fine tradition of committee perversity, Cardinal Malabranca took that as a confession of insufficient reluctance, and Pietro was dragged from his mountain and appointed Pope. He was crowned Celestine V the 29th of August 1294.
With absolutely nothing in his background to prepare him for the role, Celestine was unsurprisingly crap. The church compensated for this by largely ignoring his decisions; a fact that -- to his considerable credit -- did not escape him. Celestine made one final decree re-enforcing the right of a Pope to resign, and promptly did so. It was one decree of his that was enacted. In return for his service to the Faith, Celestine was immediately imprisioned by his successor, Boniface VIII, and died on the 19th of May, 1296, in Fumone castle.
It would be nearly 720 years before another Pope took advantage of the right to retirement.