On 10 May 1963, John XXIII received the Balzan Prize in private at the Vatican but deflected achievements of himself to the five popes of his lifetime, Pope Leo XIII to Pius XII. On 11 May, the Italian President Antonio Segni officially awarded Pope John XXIII with the Balzan Prize for his engagement for peace. While in the car en route to the official ceremony, he suffered great stomach pains but insisted on meeting with Segni to receive the award in the Quirinal Palace, refusing to do so within the Vatican. He stated that it would have been an insult to honour a pontiff on the remains of the crucified Saint Peter. It was the pope's last public appearance.

Answer this question, if possible (if impossible, reply "unanswerable"): When was Pope Pius XII officially awarded the Balzan Prize by the Italian President?
unanswerable