diff --git a/core/modules/datetime/datetime.module b/core/modules/datetime/datetime.module
index 2766607..abad5df 100644
--- a/core/modules/datetime/datetime.module
+++ b/core/modules/datetime/datetime.module
@@ -6,33 +6,33 @@
  */
 
 use Drupal\Core\Routing\RouteMatchInterface;
-use Drupal\datetime\Plugin\Field\FieldType\DateTimeItemInterface;
 
 /**
  * Defines the timezone that dates should be stored in.
  *
  * @deprecated in Drupal 8.3.x and will be removed before Drupal 9.0.x. Use
- * \Drupal\Core\Datetime\DateFormatterInterface::STORAGE_TIMEZONE instead.
+ * \Drupal\datetime\Plugin\Field\FieldType\DateTimeItemInterface::STORAGE_TIMEZONE
+ * instead.
  */
-const DATETIME_STORAGE_TIMEZONE = DateTimeItemInterface::STORAGE_TIMEZONE;
+const DATETIME_STORAGE_TIMEZONE = 'UTC';
 
 /**
  * Defines the format that date and time should be stored in.
  *
  * @deprecated in Drupal 8.3.x and will be removed before Drupal 9.0.x. Use
- * \Drupal\Core\Datetime\DateFormatterInterface::DATETIME_STORAGE_FORMAT
+ * \Drupal\datetime\Plugin\Field\FieldType\DateTimeItemInterface::DATETIME_STORAGE_FORMAT
  * instead.
  */
-const DATETIME_DATETIME_STORAGE_FORMAT = DateTimeItemInterface::DATETIME_STORAGE_FORMAT;
+const DATETIME_DATETIME_STORAGE_FORMAT = 'Y-m-d\TH:i:s';
 
 /**
  * Defines the format that dates should be stored in.
  *
  * @deprecated in Drupal 8.3.x and will be removed before Drupal 9.0.x. Use
- * \Drupal\Core\Datetime\DateFormatterInterface::DATE_STORAGE_FORMAT
+ * \Drupal\datetime\Plugin\Field\FieldType\DateTimeItemInterface::DATE_STORAGE_FORMAT
  * instead.
  */
-const DATETIME_DATE_STORAGE_FORMAT = DateTimeItemInterface::DATE_STORAGE_FORMAT;
+const DATETIME_DATE_STORAGE_FORMAT = 'Y-m-d';
 
 /**
  * Implements hook_help().
diff --git a/core/modules/datetime/src/Plugin/Field/FieldFormatter/DateTimeCustomFormatter.php b/core/modules/datetime/src/Plugin/Field/FieldFormatter/DateTimeCustomFormatter.php
index 7e65cf4..86d162d 100644
--- a/core/modules/datetime/src/Plugin/Field/FieldFormatter/DateTimeCustomFormatter.php
+++ b/core/modules/datetime/src/Plugin/Field/FieldFormatter/DateTimeCustomFormatter.php
@@ -5,6 +5,7 @@
 use Drupal\Core\Datetime\DrupalDateTime;
 use Drupal\Core\Field\FieldItemListInterface;
 use Drupal\Core\Form\FormStateInterface;
+use Drupal\datetime\Plugin\Field\FieldType\DateTimeItemInterface;
 
 /**
  * Plugin implementation of the 'Custom' formatter for 'datetime' fields.
diff --git a/core/modules/datetime/src/Plugin/Field/FieldFormatter/DateTimePlainFormatter.php b/core/modules/datetime/src/Plugin/Field/FieldFormatter/DateTimePlainFormatter.php
index 5c37122..63f7d74 100644
--- a/core/modules/datetime/src/Plugin/Field/FieldFormatter/DateTimePlainFormatter.php
+++ b/core/modules/datetime/src/Plugin/Field/FieldFormatter/DateTimePlainFormatter.php
@@ -4,6 +4,7 @@
 
 use Drupal\Core\Field\FieldItemListInterface;
 use Drupal\datetime\Plugin\Field\FieldType\DateTimeItem;
+use Drupal\datetime\Plugin\Field\FieldType\DateTimeItemInterface;
 
 /**
  * Plugin implementation of the 'Plain' formatter for 'datetime' fields.