try bugfix

diff --git a/teleforma/models/pro.py b/teleforma/models/pro.py
index b50ebe1350dc95afc97ade395bd8568fb704af2f..e89fc8cac250c0173f25fc3501ec7d8417e1bb09 100755 (executable)
--- a/teleforma/models/pro.py
+++ b/teleforma/models/pro.py
@@ -325,6 +325,6 @@ class SeminarRevision(models.Model):
 
     def delta(self):
         if self.date_modified:
-            return date_modified - date
+            return self.date_modified - self.date
         else:
             return None