diff --git a/pillarsdk/utils.py b/pillarsdk/utils.py
index 8f1e36c..7ca5f3a 100644
--- a/pillarsdk/utils.py
+++ b/pillarsdk/utils.py
@@ -22,6 +22,8 @@ else:
     string_type = basestring
     text_type = unicode
 
+JSON_DATE_FORMAT = '%a, %d %b %Y %H:%M:%S GMT'
+
 
 class PillarJSONEncoder(json.JSONEncoder):
     """JSON encoder with support for Pillar resources."""
@@ -31,7 +33,7 @@ class PillarJSONEncoder(json.JSONEncoder):
         from .resource import Resource
 
         if isinstance(obj, datetime.datetime):
-            return obj.isoformat(' ')
+            return obj.strftime(JSON_DATE_FORMAT)
         if isinstance(obj, Resource):
             return obj.to_dict()
 
diff --git a/tests/test_utils.py b/tests/test_utils.py
index eda695b..dfc8060 100644
--- a/tests/test_utils.py
+++ b/tests/test_utils.py
@@ -68,7 +68,7 @@ class PillarUtilsTests(unittest.TestCase):
         resource['datetime'] = datetime.datetime(2016, 3, 22, 12, 35, 16)
 
         as_json = json.dumps(resource, cls=utils.PillarJSONEncoder, sort_keys=True)
-        self.assertEqual('{"datetime": "2016-03-22 12:35:16"}', as_json)
+        self.assertEqual('{"datetime": "Tue, 22 Mar 2016 12:35:16 GMT"}', as_json)
 
     def test_sanitize_filename(self):