diff --git a/trello/__init__.py b/trello/__init__.py
index b7c69d37..7df736cd 100644
--- a/trello/__init__.py
+++ b/trello/__init__.py
@@ -924,7 +924,7 @@ def set_due(self, due):
 
         :title: due a datetime object
         """
-        datestr = due.strftime('%Y-%m-%d')
+        datestr = due.strftime('%Y-%m-%dT%H:%M:%S')
         self._set_remote_attribute('due', datestr)
         self.due = datestr