diff --git a/koha-tmpl/intranet-tmpl/prog/en/includes/calendar.inc b/koha-tmpl/intranet-tmpl/prog/en/includes/calendar.inc
index aba713e9cd..f6d9e9b66f 100644
--- a/koha-tmpl/intranet-tmpl/prog/en/includes/calendar.inc
+++ b/koha-tmpl/intranet-tmpl/prog/en/includes/calendar.inc
@@ -20,7 +20,7 @@ function is_valid_date(date) {
         if ( date.search(/^\d{2}\/\d{2}\/\d{4}($|\s)/) == -1 ) return 0;
         dateformat = 'dd/mm/yy';
     } else if (dateformat == 'iso' ) {
-        if ( date.search(/^\d{2}-\d{2}-\d{4}($|\s)/) == -1 ) return 0;
+        if ( date.search(/^\d{4}-\d{2}-\d{2}($|\s)/) == -1 ) return 0;
         dateformat = 'yy-mm-dd';
     } else if ( dateformat == 'dmydot' ) {
         if ( date.search(/^\d{2}\.\d{2}\.\d{4}($|\s)/) == -1 ) return 0;