2 files changed, 8 insertions, 5 deletions
diff --git a/pygithub3/resources/base.py b/pygithub3/resources/base.py
index 7045529..4c65b8b 100644
--- a/pygithub3/resources/base.py
+++ b/pygithub3/resources/base.py
@@ -1,8 +1,12 @@
 #!/usr/bin/env python
 # -*- encoding: utf-8 -*-
 
+from datetime import datetime
+
 from pygithub3.core.utils import json
 
+GITHUB_DATE_FORMAT = '%Y-%m-%dT%H:%M:%SZ'
+
 
 class Resource(object):
 
@@ -44,9 +48,8 @@ class Resource(object):
             return wrapper
 
         def parse_date(string_date):
-            from datetime import datetime
             try:
-                date = datetime.strptime(string_date, '%Y-%m-%dT%H:%M:%SZ')
+                date = datetime.strptime(string_date, GITHUB_DATE_FORMAT)
             except TypeError:
                 date = None
             return date
diff --git a/pygithub3/resources/issues.py b/pygithub3/resources/issues.py
index 69f905a..b2301a6 100644
--- a/pygithub3/resources/issues.py
+++ b/pygithub3/resources/issues.py
@@ -35,13 +35,13 @@ class Issue(Resource):
 
     _dates = ('created_at', 'updated_at', 'closed_at')
     _maps = {
-        'assignee': User, 
-        'user': User, 
+        'assignee': User,
+        'user': User,
         'milestone': Milestone,
         'pull_request': PullRequest
     }
 
-    _collection_maps = {'labels': Label} 
+    _collection_maps = {'labels': Label}
 
     def __str__(self):
         return '<Issue (%s)>' % getattr(self, 'number', '')