Better support first published date

_includes/footer.html

@@ -171,7 +171,7 @@
           ({%- include_cached t.html t="Translated:" lang=page.lang %} {{ page.translation.last_updated | date: '%Y-%m-%d' }}).
         {%- endif -%}
         {%- if page.first_published %}
-          {{ page.first_published }}
+          {%- include_cached t.html t="First published" lang=page.lang %} {{ page.first_published }}
         {%- endif -%}
         </p>
       {%- endif -%}