President of the Confederate States: Feb. 22, 1862 - May 10, 1865
U.S. Senator from Mississippi: Mar. 4, 1857 - Jan. 21, 1861
U.S. Secretary of War: Mar. 7, 1853 - Mar. 4, 1857
Member of U.S. House of Reps from Mississippi's At-large district: Dec. 8, 1845 - June 1, 1846
The answer you are looking for is most likely the date Jefferson Davis left office when he was a member of the U.S. House of Representatives (June 1, 1846), since you did not specify a certain position; this is Jefferson Davis' final leaving of office (did not return).