diff --git a/core/lib/Drupal/Component/Datetime/DateTimePlus.php b/core/lib/Drupal/Component/Datetime/DateTimePlus.php
index 2e9bc02..c849c48 100644
--- a/core/lib/Drupal/Component/Datetime/DateTimePlus.php
+++ b/core/lib/Drupal/Component/Datetime/DateTimePlus.php
@@ -23,6 +23,19 @@
  * errors are. This is less disruptive than allowing datetime exceptions
  * to abort processing. The calling script can decide what to do about
  * errors using hasErrors() and getErrors().
+ *
+ * @method DateTimePlus add(\DateInterval $interval)
+ * @method static array getLastErrors()
+ * @method DateTimePlus modify(string $modify)
+ * @method DateTimePlus setDate(int $year, int $month, int $day)
+ * @method DateTimePlus setISODate(int $year, int $week, int $day = 1)
+ * @method DateTimePlus setTime(int $hour, int $minute, int $second = 0, int $microseconds = 0)
+ * @method DateTimePlus setTimestamp(int $unixtimestamp)
+ * @method DateTimePlus setTimezone(\DateTimeZone $timezone)
+ * @method DateTimePlus sub(\DateInterval $interval)
+ * @method int getOffset()
+ * @method int getTimestamp()
+ * @method \DateTimeZone getTimezone()
  */
 class DateTimePlus {
 
diff --git a/core/lib/Drupal/Core/Datetime/DrupalDateTime.php b/core/lib/Drupal/Core/Datetime/DrupalDateTime.php
index bb7b821..80f32b8 100644
--- a/core/lib/Drupal/Core/Datetime/DrupalDateTime.php
+++ b/core/lib/Drupal/Core/Datetime/DrupalDateTime.php
@@ -17,6 +17,19 @@
  * DrupalDateTime::createFromArray( array('year' => 2010, 'month' => 9, 'day' => 28) )
  *
  * @see \Drupal/Component/Datetime/DateTimePlus.php
+ *
+ * @method DrupalDateTime add(\DateInterval $interval)
+ * @method static array getLastErrors()
+ * @method DrupalDateTime modify(string $modify)
+ * @method DrupalDateTime setDate(int $year, int $month, int $day)
+ * @method DrupalDateTime setISODate(int $year, int $week, int $day = 1)
+ * @method DrupalDateTime setTime(int $hour, int $minute, int $second = 0, int $microseconds = 0)
+ * @method DrupalDateTime setTimestamp(int $unixtimestamp)
+ * @method DrupalDateTime setTimezone(\DateTimeZone $timezone)
+ * @method DrupalDateTime sub(\DateInterval $interval)
+ * @method int getOffset()
+ * @method int getTimestamp()
+ * @method \DateTimeZone getTimezone()
  */
 class DrupalDateTime extends DateTimePlus {