diff --git a/core/modules/datetime/datetime.views.inc b/core/modules/datetime/datetime.views.inc
index b6baeb4..e6b2eb7 100644
--- a/core/modules/datetime/datetime.views.inc
+++ b/core/modules/datetime/datetime.views.inc
@@ -29,6 +29,8 @@ function datetime_field_views_data(FieldStorageConfigInterface $field_storage) {
  *
  * @return array
  *   The array of field views data with the datetime plugin.
+ *
+ * @internal
  */
 function _datetime_type_field_views_data(FieldStorageConfigInterface $field_storage, $data = [], $column_name = 'value') {
   // @todo This code only covers configurable fields, handle base table fields