diff --git a/debian/rules b/debian/rules
index 00d8596ea449a24b04832f0c0e57b911cb07dce9..460c1db3c46a06ed3432811ad27588655dd2423c 100755
--- a/debian/rules
+++ b/debian/rules
@@ -67,7 +67,7 @@ override_dh_installchangelogs:
 	dh_installchangelogs NEWS
 
 execute_before_dh_installdocs:
-	sed -i -e "s/CONTENT=\"20..-..-..T..:..:..\"/CONTENT=\"$(shell date -d "@$$SOURCE_DATE_EPOCH" "+%Y-%m-%dT%H:%M:%S")\"/" doc/src/sgml/html/*.html
+	sed -i -e "s/CONTENT=\"20..-..-..T..:..:..\"/CONTENT=\"$(shell date -ud "@$$SOURCE_DATE_EPOCH" "+%Y-%m-%dT%H:%M:%S")\"/" doc/src/sgml/html/*.html
 
 %:
 	dh $@