For the debian version to sort properly you actually need to use Ymd format.

shalasz · shalasz · commit 2b86361814bd · 2006-06-17T01:28:05.000Z
git-svn-id: http://svn.osgeo.org/qgis/trunk/qgis@5527 c8812cc2-4d05-0410-92ff-de0c093fc19c
diff --git a/build_debian_package.sh b/build_debian_package.sh
@@ -20,5 +20,5 @@ fi
 
 export DEBFULLNAME="Tim Sutton"
 export DEBEMAIL=tim@linfiniti.com
-dch -v 0.7.9+svn`date +%m%d%Y`
+dch -v 0.7.9+svn`date +%Y%m%d`
 fakeroot dpkg-buildpackage
