Five million pilgrims are expected in Rome for the canonisation of two popes, John XXIII and John Paul II.
Equally historic is the possibility that two living popes will celebrate at the ceremony, Pope Francis and Pope Emeritus Benedict XVI.
Pope John Paul's cause for sainthood was evident at his funeral, with banners proclaiming "Santo Subito" or "sainthood now".
Normally, two miracles attributed to the deceased need to be verified. The first for John Paul II was a French nun, said to be cured of Parkinson's. The second was a Costa Rican woman, cured of a brain aneurism.
In the sainthood of Pope John XXIII, the process has been different. The Church attributes only one miracle to his intercession but Pope Francis made an exception. John XXIII, often referred to as "Good Pope John", through his calling of the council changed the way the Church relates to the world and other religions.
As The Tablet says this week, "There is little doubt that the two most outstanding Popes of the past 100 years were John XXIII and John Paul II," but other popes such as Leo XIII and Benedict XV who have not been canonised are "no less worthy of admiration and respect".
Lives at a glance
John Paul II
25 November 1881, Sotto il Monte, Bergamo, Italy
18 May 1920, Wadowice, Poland
Angelo Giuseppe Roncalli
Karol Józef Wojtyla
28 October 1958 after 11 ballots
16 October 1978 after eight ballots
4 years 7 months 5 days
26 years 5 months 17 days
3 June 1963
2 April 2005
Calling the Second Vatican Council, Pacem in Terris, removing the word 'perfidious' from Good Friday prayer for the Jews
First Polish Pope, taking on communism, improving ties with Jews, clamping down on Liberation theology, notably on visit to Nicaragua in 1983
Obedientia et pax - 'obedience and peace'
Totus tuus – 'totally yours', an expression of his Marian devotion
Especially popular with
Progressives, social justice activists, Italians
Weakening the Church because the Council reforms coincided with falling numbers of vocations and laity
Turning a blind eye to burgeoning abuse crisis Insisting on universal ban on condoms even in face of rising HIV epidemic
Worked in Bulgaria, Turkey, Greece and France before being elected pope; thereafter remained in Italy
Remained mostly in Poland before election; as Pope travelled to 129 countries
3 September 2000, by Pope John Paul II
1 May 2011, by Pope Benedict XVI
11 October 4 June (Anglican Communion)
Did you know?
Pope John would leave the Vatican to walk the streets of Rome to be with the people
As a boy, Karol would offer to be in goal for the Jewish football side if a group of Catholics and a group of Jewish boys wanted to take each other on