Pope John Paul II became the third longest-reigning pontiff in the history of the Roman Catholic church since the post was first taken by one of Jesus Christ's Apostles, Simon Peter, who reigned for at least 34 years.
The current pope, who is due to turn 84 in May, has served for 25 years, four months and 18 days since his election in October 1978, surpassing the reign of Leo XIII, who occupied the Vatican from 1878 to 1903.
However the pontiff, who suffers from crippling Parkinson's disease, still has some way to go to surpass the second longest reign -- Leo XIII's predecessor Pius IX, who served more than 31 years between June 1846 and February 1878.
The occasion was due to pass without the pomp and ceremony with which the Vatican marked the 25th anniversary of John Paul II's pontificate last October, but it illustrates the remarkable resilience of John Paul II, who is beset by serious health problems.
John Paul II celebrated the Angelus prayers as usual, in the Vatican's Saint Peter's Square, and took time to condemn Thursday's train bombings in Madrid which killed 200 and injured 1,500.
"This horrible crime has shocked world public opinion. Before so much barbarity, we remain profoundly shaken, and wonder how the human spirit can conceive of such detestable actions," the pope said, speaking before thousands on St Peter's Square.
"In reiterating my absolute condemnation of such unjustifiable acts, I once again express my participation in the pain of the victims' families," he told the crowd of faithful, some of whom were waving Spanish flags.
John Paul II said it was by bringing together "all the healthy forces on the continent that we can look forward with trust and hope for a better future."
The official church record for the longest-reigning pope goes to Simon Peter of Galilee, the first of Jesus's apostles, to whom He personally entrusted the wellbeing of the Church before the crucifixion.
Historians are divided over whether Peter served 34 or 37 years as the first pope -- and some even doubt that he existed at all.
In that case -- not one contemplated by the Vatican which houses what Christians believe is Peter's tomb -- John Paul II's would be the second longest pontificate.
The fact that John Paul II has lived to reach such a milestone has astonished Vatican watchers who marvel at his repeated ability to rally despite his debilitating illnesses.
Only six months ago, in the run-up to the October consistory held to elevate 30 new cardinals, senior cardinals appeared to be preparing the Catholic faithful for the pope's demise.
At the time, he appeared particularly weak due to the treatment for his illness. The Parkinson's disease which he has suffered for more than a decade has left him almost immobile, short of breath, and at times, even unable to speak.
But John Paul II's improved health in recent months has led to increasing speculation that he may be prepared to resume limited foreign travel, unthinkable just a few months ago.
According to Sunday's issue of La Repubblica newspaper, the pope has started walking again, helped by his physiotherapists, in the past few days.