diff --git a/moulinette/utils/serialize.py b/moulinette/utils/serialize.py
index bc0e6d1d..800cf1b0 100644
--- a/moulinette/utils/serialize.py
+++ b/moulinette/utils/serialize.py
@@ -1,5 +1,6 @@
 import logging
 from json.encoder import JSONEncoder
+import datetime
 
 logger = logging.getLogger('moulinette.utils.serialize')
 
@@ -24,6 +25,10 @@ class JSONExtendedEncoder(JSONEncoder):
                 hasattr(o, '__iter__') and hasattr(o, 'next')):
             return list(o)
 
+        # Display the date in its iso format ISO-8601 Internet Profile (RFC 3339)
+        if isinstance(o, datetime.datetime) or isinstance(o, datetime.date):
+            return o.isoformat()
+
         # Return the repr for object that json can't encode
         logger.warning('cannot properly encode in JSON the object %s, '
                        'returned repr is: %r', type(o), o)