It's about as long as Pius IX's reign.
(a.k.a. Pope Blessed Pius IX, a.k.a. Giovanni Maria Mastai-Ferretti) (1792-1878)
The longest reigning Pope in the Church's history, Pius IX reigned from June 16th, 1846 to February 7th, 1878 — 3.165 decades. As the last monarchical Pope, he ruled over 3,000,000 subjects in the Papal States until 1870.
It's about two-and-a-half times as long as FDR's Presidential Term.
In other words, 3.165 decades is 2.614 times the length of FDR's Presidential Term, and the length of FDR's Presidential Term is 0.3826 times that amount.(a.k.a. Franklin Roosevelt, a.k.a. Franklin Delano Roosevelt) (1933-45)
It's about three times as long as King Tut's reign.
In other words, the length of King Tut's reign is 0.3 times 3.165 decades.(a.k.a. Tutankhamun, a.k.a. Tutankhaten, a.k.a. tVwa:t-ʕa:nəx-ʔaˡma:n) (1333 BCE - 1324 BCE)
It's about three-tenths as long as Pepi II's reign.
In other words, the length of Pepi II's reign is 3 times 3.165 decades.(a.k.a. Neferkare) (2278 BCE - 2184 BCE)
It's about four times as long as The Revolutionary War (American).
In other words, 3.165 decades is 3.778 times the length of The Revolutionary War (American), and the length of The Revolutionary War (American) is 0.2647 times that amount.(a.k.a. American War of Independence) (1775-83)
It's about five times as long as The Construction of the Chunnel.
In other words, 3.165 decades is 4.954 times the length of The Construction of the Chunnel, and the length of The Construction of the Chunnel is 0.2019 times that amount.(a.k.a. Channel Tunnel, a.k.a. Le tunnel sous la Manche) (1987 thru 1994) (Folkstone, Kent, UK to Coquelles, Pas-de-Calais, France)
It's about five-and-a-half times as long as World War II.
In other words, 3.165 decades is 5.271 times the length of World War II, and the length of World War II is 0.1897 times that amount.(a.k.a. Second World War, a.k.a. WWII, a.k.a. WW2) (1939 - 1945)