core/modules/serialization/serialization.services.yml          | 1 +
 core/tests/Drupal/Tests/Listeners/DeprecationListenerTrait.php | 1 +
 2 files changed, 2 insertions(+)

diff --git a/core/modules/serialization/serialization.services.yml b/core/modules/serialization/serialization.services.yml
index c883410..1eb3aa1 100644
--- a/core/modules/serialization/serialization.services.yml
+++ b/core/modules/serialization/serialization.services.yml
@@ -65,6 +65,7 @@ services:
       - { name: normalizer, priority: 20, bc: bc_timestamp_normalizer_unix, bc_config_name: 'serialization.settings' }
   serializer.normalizer.datetimeiso8601:
     class: \Drupal\serialization\Normalizer\DateTimeIso8601Normalizer
+    deprecated: The "%service_id%" service is deprecated and will be removed in Drupal 9.0.0.
     tags:
       # Priority must be higher than serializer.normalizer.primitive_data.
       - { name: normalizer, priority: 20 }
diff --git a/core/tests/Drupal/Tests/Listeners/DeprecationListenerTrait.php b/core/tests/Drupal/Tests/Listeners/DeprecationListenerTrait.php
index 216f900..bcaba0b 100644
--- a/core/tests/Drupal/Tests/Listeners/DeprecationListenerTrait.php
+++ b/core/tests/Drupal/Tests/Listeners/DeprecationListenerTrait.php
@@ -187,6 +187,7 @@ public static function getSkippedDeprecations() {
       'The "session_handler.write_check" service relies on the deprecated "Symfony\Component\HttpFoundation\Session\Storage\Handler\WriteCheckSessionHandler" class. It should either be deprecated or its implementation upgraded.',
       'Not setting the strict option of the Choice constraint to true is deprecated since Symfony 3.4 and will throw an exception in 4.0.',
       'Using the Yaml::PARSE_KEYS_AS_STRINGS flag is deprecated since Symfony 3.4 as it will be removed in 4.0. Quote your keys when they are evaluable instead.',
+      'The "serializer.normalizer.datetimeiso8601" service is deprecated and will be removed in Drupal 9.0.0.'
     ];
   }