Question: What is the birthday of the pope who promulgated the Romano Pontifici eligendo?

full_context: Document 1: Pope Paul VI: Pope Paul VI (Latin: Paulus VI; Italian: Paolo VI), born Giovanni Battista Enrico Antonio Maria Montini (Italian pronunciation: [dʒioˈvani baˈtista enˈriko anˈtonjo marˈija monˈtini]; 26 September 1897 – 6 August 1978), reigned as Pope from 21 June 1963 to his death in 1978. Succeeding Pope John XXIII, he continued the Second Vatican Council which he closed in 1965, implementing its numerous reforms, and fostered improved ecumenical relations with Eastern Orthodox and Protestants, which resulted in many historic meetings and agreements. Montini served in the Vatican's Secretariat of State from 1922 to 1954. While in the Secretariat of State, Montini and Domenico Tardini were considered as the closest and most influential colleagues of Pope Pius XII, who in 1954 named him Archbishop of Milan, the largest Italian diocese. Montini automatically became the Secretary of the Italian Bishops Conference. John XXIII elevated him to the College of Cardinals in 1958, and after the death of John XXIII, Montini was considered one of his most likely successors.
Document 2: Pope John XXIII: The Roman Catholic Church celebrates his feast day not on the date of his death, June 3, as is usual, nor even on the day of his papal inauguration (as is sometimes done with Popes who are Saints, such as with John Paul II) but on 11 October, the day of the first session of the Second Vatican Council. This is understandable, since he was the one who had had the idea for it and had convened it. On Thursday, 11 September 2014, Pope Francis added his optional memorial to the worldwide General Roman Calendar of saints' feast days, in response to global requests. He is commemorated on the date of his death, 3 June, by the Evangelical Lutheran Church in America and on the following day, 4 June, by the Anglican Church of Canada and the Episcopal Church (United States).
Document 3: Cardinal (Catholic Church): In early times, the privilege of papal election was not reserved to the cardinals, and for centuries the person elected was customarily a Roman priest and never a bishop from elsewhere. To preserve apostolic succession the rite of consecrating him a bishop had to be performed by someone who was already a bishop. The rule remains that, if the person elected Pope is not yet a bishop, he is consecrated by the Dean of the College of Cardinals, the Cardinal Bishop of Ostia.
Document 4: Pope Paul VI: With the six consistories, Paul VI continued the internationalization policies started by Pius XII in 1946 and continued by John XXIII. In his 1976 consistory, five of twenty cardinals originated from Africa, one of them a son of a tribal chief with fifty wives. Several prominent Latin Americans like Eduardo Francisco Pironio of Argentina; Luis Aponte Martinez of Puerto Rico and Eugênio de Araújo Sales and Aloisio Lorscheider from Brazil were also elevated by him. There were voices within the Church at the time saying that the European period of the Church was coming to a close, a view shared by Britain's Cardinal Basil Hume. At the same time, the members of the College of Cardinals lost some of their previous influences, after Paul VI decreed, that not only cardinals but also bishops too may participate in committees of the Roman Curia. The age limit of eighty years imposed by the Pope, a numerical increase of Cardinals by almost 100%, and a reform of the regal vestments of the "Princes of the Church" further contributed to a service-oriented perception of Cardinals under his pontificate. The increased number of Cardinals from the Third World and the papal emphasis on related issues was nevertheless welcomed by many in Western Europe.
Document 5: Pope Paul VI: In December 2013, Vatican officials approved a supposed miracle that was attributed to the intercession of the late pontiff which was the curing of an unborn child in California, U.S.A in the 1990s. It was expected that Pope Francis would approve the miracle in the near future, thus, warranting the beatification of the late pontiff. In February 2014, it was reported that the consulting Vatican theologians to the Congregation for the Causes of Saints recognized the miracle attributed to the late pontiff.
Document 6: Cardinal (Catholic Church): Pope Sixtus V limited the number of cardinals to 70, comprising six cardinal bishops, 50 cardinal priests, and 14 cardinal deacons. Starting in the pontificate of Pope John XXIII, that limit has been exceeded. At the start of 1971, Pope Paul VI set the number of cardinal electors at a maximum of 120, but set no limit on the number of cardinals generally. He also established a maximum age of eighty years for electors. His action deprived twenty-five living cardinals, including the three living cardinals elevated by Pope Pius XI, of the right to participate in a conclave.[citation needed] Popes can dispense from church laws and have sometimes brought the number of cardinals under the age of 80 to more than 120. Pope Paul VI also increased the number of cardinal bishops by giving that rank to patriarchs of the Eastern Catholic Churches.
Document 7: Pope Paul VI: Paul VI revolutionized papal elections by ordering that only cardinals below the age of eighty might participate in future conclaves. In Ecclesiae Sanctae, his motu proprio of 6 August 1966, he further invited all bishops to offer their retirement to the pontiff no later than the completion of their 75th year of age. This requirement was extended to all Cardinals of the Catholic Church on 21 November 1970. With these two stipulations, the Pope filled several positions with younger bishops and cardinals, and further internationalized the Roman Curia in light of several resignations due to age.
Document 8: Pope John XXIII: Many had considered Giovanni Battista Montini, the Archbishop of Milan, a possible candidate, but, although he was the archbishop of one of the most ancient and prominent sees in Italy, he had not yet been made a cardinal. Though his absence from the 1958 conclave did not make him ineligible – under Canon Law any Catholic male who is capable of receiving priestly ordination and episcopal consecration may be elected – the College of Cardinals usually chose the new pontiff from among the Cardinals who head archdioceses or departments of the Roman Curia that attend the papal conclave. At the time, as opposed to contemporary practice, the participating Cardinals did not have to be below age 80 to vote, there were few Eastern-rite Cardinals, and no Cardinals who were just priests at the time of their elevation.
Document 9: Pope Paul VI: Pius XII delivered an address about Montini's appointment from his sick-bed over radio to those assembled in St. Peter's Basilica on 12 December 1954. Both Montini and the pope had tears in their eyes when Montini parted for his dioceses with 1,000 churches, 2,500 priests and 3,500,000 souls. On 5 January 1955, Montini formally took possession of his Cathedral of Milan. Montini, after a period of preparation, liked his new tasks as archbishop, connecting to all groups of faithful in Milan. He enjoyed meetings with intellectuals, artists and writers.
Document 10: Pope Paul VI: On 20 December 2012, Pope Benedict XVI, in an audience with the Cardinal Prefect of the Congregation for the Causes of Saints, declared that the late pontiff had lived a life of heroic virtue, which means that he could be called "Venerable". A miracle attributed to the intercession of Paul VI was approved on 9 May 2014 by Pope Francis. The beatification ceremony for Paul VI was held on 19 October 2014, which means that he can now be called "Blessed". His liturgical feast day is celebrated on the date of his birth, 26 September, rather than the day of his death as is usual.
Document 11: Romano Pontifici eligendo: Romano Pontifici eligendo was the apostolic constitution governing the election of popes that was promulgated by Pope Paul VI in 1 October 1975. It instituted a number of far-reaching reforms in the process of electing popes. It set the maximum number of electors at 120 and restated in a more formal context the rule he had already instituted that cardinals over the age of 80 not participate in electing a pope.
Document 12: Pope John XXIII: Roncalli was summoned to the final ballot of the conclave at 4:00 pm. He was elected pope at 4:30 pm with a total of 38 votes. After the long pontificate of Pope Pius XII, the cardinals chose a man who – it was presumed because of his advanced age – would be a short-term or "stop-gap" pope. They wished to choose a candidate who would do little during the new pontificate. Upon his election, Cardinal Eugene Tisserant asked him the ritual questions of whether he would accept and if so, what name he would take for himself. Roncalli gave the first of his many surprises when he chose "John" as his regnal name. Roncalli's exact words were "I will be called John". This was the first time in over 500 years that this name had been chosen; previous popes had avoided its use since the time of the Antipope John XXIII during the Western Schism several centuries before.
Document 13: Pope Paul VI: On 24 April 2014, it was reported in the Italian magazine Credere that the late pope could possibly be beatified on 19 October 2014. This report from the magazine further stated that several cardinals and bishops would meet on 5 May to confirm the miracle that had previously been approved, and then present it to Pope Francis who may sign the decree for beatification shortly after that. The Congregation for the Causes of Saints held that meeting and positively concluded that the healing was indeed a miracle that could be attributed to the late pope. The matter shall now soon be presented to the pope for approval.
Document 14: Pope Paul VI: Paul VI supported the new-found harmony and cooperation with Protestants on so many levels. When Cardinal Augustin Bea went to see him for permission for a joint Catholic-Protestant translation of the Bible with Protestant Bible societies, the pope walked towards him and exclaimed, "as far as the cooperation with Bible societies is concerned, I am totally in favour." He issued a formal approval on Pentecost 1967, the feast on which the Holy Spirit descended on the Christians, overcoming all linguistic difficulties, according to Christian tradition.
Document 15: Pope John XXIII: The 50th anniversary of his death was celebrated on 3 June 2013 by Pope Francis, who visited his tomb and prayed there, then addressing the gathered crowd and spoke about the late pope. The people that gathered there at the tomb were from Bergamo, the province where the late pope came from. A month later, on 5 July 2013, Francis approved Pope John XXIII for canonization, along with Pope John Paul II without the traditional second miracle required. Instead, Francis based this decision on John XXIII's merits for the Second Vatican Council. On Sunday, 27 April 2014, John XXIII and Pope John Paul II were declared saints on Divine Mercy Sunday.
ground_truth: 26 September
sub_queries: Romano Pontifici Eligendo >> author Answer: Paul VI
On what day was Paul VI born? Answer: 26 September