--- a/src/pyams_workflow/content.py	Fri May 24 09:02:27 2019 +0200
+++ b/src/pyams_workflow/content.py	Wed Jun 17 13:54:56 2020 +0200
@@ -58,7 +58,7 @@
                 if info is not None and info.publication_effective_date:
                     first_version_label = '{1} (= {0})'.format(first_version_label.lower(),
                                                                format_date(info.publication_effective_date,
-                                                                           format=SH_DATE_FORMAT))
+                                                                           format_string=SH_DATE_FORMAT))
             terms.append(SimpleTerm(DISPLAY_FIRST_VERSION, title=first_version_label))
         # check for current version
         current_version_label = request.localizer.translate(VERSION_DISPLAY[DISPLAY_CURRENT_VERSION])
@@ -66,7 +66,7 @@
         if info is not None and info.publication_effective_date:
             current_version_label = '{1} (= {0})'.format(current_version_label.lower(),
                                                          format_date(info.publication_effective_date,
-                                                                     format=SH_DATE_FORMAT))
+                                                                     format_string=SH_DATE_FORMAT))
         terms.append(SimpleTerm(DISPLAY_CURRENT_VERSION, title=current_version_label))
         super(WorkflowContentDisplayedDateVocabulary, self).__init__(terms)