It was confirmed that TWD: Michonne takes lace in the later half of 2005. In TWD: Michonne, Paige says that about a year ago, Sophia Fairbanks took her life, that means Sophia died in 2004, and according to Sophia's wiki page, that happened, 3 years into the apocalypse. That means The Outbreak happened in 2001, together with the date revealed in Around Every Corner, says that the full date of the outbreak is July 20th, 2001, I don't know why some wiki pages state, that the outbreak happened in 2003.