diff --git a/wagtail/wagtailadmin/static/wagtailadmin/js/page-editor.js b/wagtail/wagtailadmin/static/wagtailadmin/js/page-editor.js
index a8d492ffc..af624572e 100644
--- a/wagtail/wagtailadmin/static/wagtailadmin/js/page-editor.js
+++ b/wagtail/wagtailadmin/static/wagtailadmin/js/page-editor.js
@@ -56,20 +56,23 @@ function insertRichTextDeleteControl(elem) {
 function initDateChooser(id) {
     $('#' + id).datetimepicker({
         timepicker: false,
-        format: 'Y-m-d'
+        format: 'Y-m-d',
+        mask: '9999-19-39'
     });
 }
 
 function initTimeChooser(id) {
     $('#' + id).datetimepicker({
         datepicker: false,
-        format: 'H:i'
+        format: 'H:i:s',
+        mask: '29:59:59'
     });
 }
 
 function initDateTimeChooser(id) {
     $('#' + id).datetimepicker({
-        format: 'Y-m-d H:i'
+        format: 'Y-m-d H:i:s',
+        mask: '9999-19-39 29:59:59'
     });
 }