http://www.moveon.org/mediacorps/mediacorps29.html
"Bush was apparently absent without official leave from his assigned military service for as little as seven months (New York Times) or as much as 17 months (Boston Globe) during a time when 500,000 American troops were fighting the Vietnam War. The Army defines a “deserter” -- also known as a DFR, for “dropped from rolls” -- as one who is AWOL 31 days or more: www-ari.army.mil/pdf/s51.pdf."
Chris