Donut-Time USA was a donut store in Ann Arbor, MI at 2307 W Stadium Blvd in 1974. It is now closed.
http://www.aadl.org/gallery/pictureAnnArbor/a2signs/A2signs467.jpg.html
An additional hint comes from a University of Michigan student directory of 1973, which lists a location at 4837 Washtenaw Ave.