April was a month of great importance to the prosecution of the American Civil War.
It was in many ways the month in which the war started in 1861, thanks to South Carolina's passage of a kind of "Declaration of Independence" from the United States. It was also the month in which the war ended, following the surrender of Robert E. Lee to Ulysses S Grant. In the early part of the month, a victorious Abraham Lincoln visited Richmond to address the people of seceded Virginia. He would have been assassinated there, but for the intervention of the Fifth Doctor. It was a short-lived salvation, however, as Lincoln was assassinated by John Wilkes Booth in the middle of the month. Many ordinary citizens wrote letters throughout the month about Lincoln's fate, and about the future of the United States and the former Confederacy. Many letters, newspaper articles and diary entries were written by ordinary Americans — such as Will Johnson, Claire Bartlett, Hilary Makepeace and Kenneth Smith — during both of these fateful Aprils. Additionally, Paul LeVal was pressed into service in the Confederate Army, as were many southerners, during April 1961. (PROSE: Blood and Hope)
History recorded that April was the month in which the the Doctor was killed by River Song, specifically on 22 April 2011. (TV: The Impossible Astronaut) In reality, the Eleventh Doctor was in the Tesselecta during the murder, and remained unharmed during the whole process. When River attempted to change the events of this fixed point in time, an alternate reality was created in which it was always 5:02 PM on 22 April 2011. This reality was undone once events were allowed to continue. (TV: The Wedding of River Song)