Only support iso8601 for older drafts.

Julian · Julian · commit 2e16ebecd2dd · 2017-10-29T17:21:53.000-04:00
diff --git a/jsonschema/_format.py b/jsonschema/_format.py
@@ -221,7 +221,8 @@ def is_uri(instance):
         pass
     else:
         @_checks_drafts(
-            name="date-time",
+            draft3="date-time",
+            draft4="date-time",
             raises=(ValueError, isodate.ISO8601Error),
         )
         def is_datetime(instance):
