So the Civil War ended on April 9th 1865, Lincoln is assassinated on April 14th 1865 and the Titanic sank on April 15th 1912. Coincidence - I think not.
Also, the US entered WW1 on April 6th 1917 after the Lusitainia was sunk, on April 10th, 1945 Buchenwald was liberated, on April 12th 1861...