--- a/src/pyams_utils/date.py	Wed May 20 12:41:37 2015 +0200
+++ b/src/pyams_utils/date.py	Wed Jun 17 10:01:29 2015 +0200
@@ -81,6 +81,8 @@
 
 def format_date(value, format=EXT_DATE_FORMAT, request=None):
     """Format given date with the given format"""
+    if not value:
+        return '--'
     if request is None:
         request = check_request()
     localizer = request.localizer