diff -u b/core/lib/Drupal/Component/Datetime/DateTimePlus.php b/core/lib/Drupal/Component/Datetime/DateTimePlus.php
--- b/core/lib/Drupal/Component/Datetime/DateTimePlus.php
+++ b/core/lib/Drupal/Component/Datetime/DateTimePlus.php
@@ -284,6 +284,8 @@
   }
 
   /**
+   * Implements the magic __call method.
+   *
    * Passes through all unknown calls onto the DateTime object.
    */
   public function __call($method, $args) {
@@ -298,6 +300,8 @@
   }
 
   /**
+   * Implements the magic __callStatic method.
+   *
    * Passes through all unknown static calls onto the DateTime object.
    */
   public static function __callStatic($method, $args) {
@@ -308,6 +312,8 @@
   }
 
   /**
+   * Implements the magic __clone method.
+   *
    * Deep-clones the DateTime object we're wrapping.
    */
   public function __clone() {