His inauguration mass was held on April 24, 2005.
Pope John XXIII was ordained pope on October 28th, 1958
Benedict became pope the instant he accepted the position after the final ballot was taken on April 19, 2005. He was installed as pope on April 25.
not cooperate with the new government
he had lost control of the papal states
Canon Law only states that the person be a male Catholic. However, if he is not already a priest or bishop, he must be ordained as both before he can be installed as pope.
they did not cooperate with the new government
He was elected pope by the College of Cardinals after his father had, essentially, purchased the papacy for him and had him installed as pope. He is, undoubtedly, one of the worst and most vile of men to ever rule as pope. He actually was three times as pope before he was eventually excommunicated and sent packing by the legitimately elected Pope Damascus II. For more information on this sordid story click here.
Pope Urban VII (Sep 15-27, 1590) served only 13 days and is the shorted reigning pope. Pope Elect Stephen died 2 days after the papal election but was never installed as pope so he doesn't count. He was not a bishop and could not assume the papacy until he was consecrated as bishop.
Before your question can be answered, you need to clarify two points:1.) To which of the 266 popes over the history of the papacy do you refer?2.) Do you mean when he was ordained a priest, a bishop or installed as pope?
The man elected as pope does not have to be ordained. However, once he is elected as pope he must be ordained as a bishop before he can be installed as pope. An example is Pope Elect Stephen II. He was a layman who was elected as pope. Before he could be made a bishop, however, he died, just two days after his election. Therefore, having never been a bishop, he is not considered to have been a pope,
On April 24, 2005, Benedict celebrated the Papal Inauguration Mass in St. Peter's Square.