Howling:History after the Time Crack

It's been said that a lot of the 21st century alien invasions have been unwritten from time by the Time Crack. So if the Sycorax attack in "The Christmas Invasion" never happened, how do people explain the deaths and Harriet Jones getting deposed? If the Dalek invasion in "The Stolen Earth/Journey's End" never happened, how do people explain the worldwide carnage and destruction that resulted? How does Wilf explain how Donna came back home after travelling with the Doctor? EJA 21:13, May 10, 2011 (UTC)