--- a/src/pyams_content/shared/common/zmi/summary.py	Fri Oct 13 08:38:14 2017 +0200
+++ b/src/pyams_content/shared/common/zmi/summary.py	Fri Oct 13 08:38:32 2017 +0200
@@ -181,7 +181,7 @@
         state = IWorkflowState(self.context)
         pub_date = tztime(state.get_first_state_date(workflow.published_states))
         if pub_date is None:
-            value = '--'
+            value = ''
         else:
             now = tztime(datetime.utcnow())
             pub_info = IWorkflowPublicationInfo(self.context)
@@ -189,7 +189,7 @@
                 value = format_datetime(tztime(pub_date))
             else:
                 if pub_info.publication_effective_date < now:
-                    value = '--'
+                    value = ''
                 else:
                     value = format_datetime(tztime(pub_info.publication_effective_date))
         self.widgets['first_publication_date'].value = value