Ticket #1584: auto_now_add_fix.diff

django/db/models/fields/__init__.py

@@ -423 +423 @@
         return Field.get_db_prep_lookup(self, lookup_type, value)
 
     def pre_save(self, value, add):
-        if self.auto_now or (self.auto_now_add and add):
+        if self.auto_now or (not value and self.auto_now_add and add):
             return datetime.datetime.now()
         return value