diff --git a/kallithea/lib/feeds.py b/kallithea/lib/feeds.py
--- a/kallithea/lib/feeds.py
+++ b/kallithea/lib/feeds.py
@@ -57,7 +57,7 @@ def get_tag_uri(url, date):
     "Creates a TagURI. See http://diveintomark.org/archives/2004/05/28/howto-atom-id"
     tag = re.sub('^http://', '', url)
     if date is not None:
-        tag = re.sub('/', ',%s:/' % date.strftime('%Y-%m-%d'), tag, 1)
+        tag = re.sub('/', ',%s:/' % date.strftime('%Y-%m-%d'), tag, count=1)
     tag = re.sub('#', '/', tag)
     return 'tag:' + tag