diff --git a/elfutils.spec b/elfutils.spec
index 68bd3d8..2a6647b 100644
--- a/elfutils.spec
+++ b/elfutils.spec
@@ -145,6 +145,8 @@ to develop applications that require these.
 %patch7 -p1
 
 %build
+# Change DATE/TIME macros to use last change time of elfutils.changes
+# See http://lists.opensuse.org/opensuse-factory/2011-05/msg00304.html
 modified="$(sed -n '/^----/n;s/ - .*$//;p;q' "%{_sourcedir}/%{name}.changes")"
 DATE="\"$(date -d "${modified}" "+%%b %%e %%Y")\""
 TIME="\"$(date -d "${modified}" "+%%R")\""