Pope Stephen II was elected on 24 March 752 following the death of Pope Zacharias (reigned 741–752) and died two days later.
In more recent years, the shortest pontificates have been as follows:-
Leo XI (1 April – 12 April 1605) – 11 days
Pope Urban VII (15 – 27 September 1590) – 12 days
Marcellus II (9 April – 1 May 1555) – 20 days
John Paul 1 (26 August – 28 September 1978) – 23 days
Pius II (22 September – 18 October 1503) – 26 days