In Season 4, it is stated that Booth has been in the FBI for twelve years, which implies that he would have joined the Bureau around 1996. However, this contradicts his statements in Season 6 about going AWOL to be present at the birth of his son, Parker (Parker was four when the show premiered in 2005) and in season 10 when he recounts to Wendell Bray of watching his men getting shot and killed by the Taliban during a mission in Ghazni, Afghanistan (American troops did not enter Afghanistan until after the attacks on September 11, 2001). A possible realistic explanation would be that Booth remained in the Army as a reservist.