Let's take Postmodern out of the picture for a second...
CL-USER> (decode-universal-time (get-universal-time)) 19 28 8 16 11 2010 1 NIL -1 CL-USER> (dotimes (i 1) (decode-universal-time (get-universal-time))) NIL
See the pattern?
A loop doesn't return the value of its body, typically, since that body will be executed multiple times.