Aggiornamento (Italian pronunciation: [addʒɔrnaˈmento]), a.k.a. "A bringing up to date", was one of the key words used during the Second Vatican Council both by bishops and the clergy attending the sessions, and by the media and Vaticanologists covering it. It was used to mean a spirit of change and open-mindedness. It was the name given to the pontifical program of John XXIII in a speech he gave on January 25, 1959.
Before the council 
Originally, the word referred merely to an adjournment of the Code of Canon law, as John XXIII said himself in his 1959 speech. However, the Code of canon law was only completed in 1983, after a long delay of 18 years after the end of the Council. The Canon law project was soon broadened into a larger process of Church reform.
In June 1961, in an address to a group of Blessed Sacrament Fathers, John XXIII said
The ecumenical council will reach out and embrace under the widespread wings of the Catholic Church the entire heredity of Our Lord Jesus Christ. Its principal task will be concerned with the condition and modernization (in Italian: aggiornamento) of the Church after 20 centuries of life. May it be that side by side with this, God will add also, through whatever edification we may offer, but above all by merit of the omnipotence of the Most High who can draw new chosen sons from the very stones, one other result: a movement toward recomposition of the whole Mystical Flock of Our Lord.
Gaudium et Spes 
The conciliar document most often associated with the aggiornamento is Gaudium et Spes. The document was not drafted before the council met, but arose from the floor of the council and was one of the last to be promulgated.
Yves Congar 
French theologian Yves Congar was a lead reformist during the Council, which he even described as an October Revolution in the Church. Congar, who had previously been condemned by the Holy Office, was invited to the Council, where he played a significant role in the discussions between the Curial minority and the Episcopal majority.
Many clergy could be categorised as belonging to either camp. Aggiornamentos were seen as looking to the future in a post-Tridentine Church, while ressourcement members were seen as attempting to look back to the church before Trent for a simpler liturgy and less Rome-orientated leadership style.
Neither was satisfied with the Church as it stood immediately before the Council. Both however sought inspiration for the expected new style conciliar church in different eras.
Paul VI 
Paul VI went on to adopt Pope John's motto for himself, as he stated in Ecclesiam Suam : We cannot forget Pope John XXIII's word aggiornamento which We have adopted as expressing the aim and object of Our own pontificate. Besides ratifying it and confirming it as the guiding principle of the Ecumenical Council, We want to bring it to the notice of the whole Church. It should prove a stimulus to the Church to increase its ever growing vitality and its ability to take stock of itself and give careful consideration to the signs of the times, always and everywhere "proving all things and holding fast that which is good" with the enthusiasm of youth.
Conservative reaction 
Some conservatives had warned about excessive progressivism and had repeated the final sentence of the 1861 Syllabus of Errors : The Roman Pontiff can, and ought to, reconcile himself, and come to terms with progress, liberalism and modern civilization.
Cardinal Francis Spellman, who had been nominated by Pius XII, was reportedly cautious of aggiornamento and, before departing to Rome, declared, "No change will get past the Statue of Liberty." The Cardinal believed that predominantly liberal clergymen were being appointed to the Council's commissions, and opposed the introduction of vernacular into the Mass, saying, "The Latin language, which is truly the Catholic language, is unchangeable, is not vulgar, and has for many centuries been the guardian of the unity of the Western Church."
John Paul II 
Aggiornamentos were particularly associated with the much repeated phrase in the Church in the 1960s the sign of the times, meaning an attempt to learn from the world and read the 'signs of the times'.
The theological method of Pope John Paul II represented an attempt to wed the two concepts by drawing upon the ancient deposit of faith to address contemporary issues in an engaging way.
- Allocuzione con la quale il Sommo Pontefice annuncia il Sinodo Romano, il Concilio Ecumenico e l'aggiornamento del Codice di diritto Canonico
- "Pope speaks of unity and the Council". The Criterion (Archdiocese of Indianapolis). 7 July 1961.
- The Destruction of Christian Tradition