.../EntityResource/EntityTest/EntityTestDateRangeTest.php   |  8 +++-----
 core/modules/hal/src/Normalizer/TimestampItemNormalizer.php |  3 ++-
 .../src/Normalizer/DateTimeIso8601Normalizer.php            |  4 ++--
 .../src/Unit/Normalizer/DateTimeIso8601NormalizerTest.php   | 13 ++++++-------
 4 files changed, 13 insertions(+), 15 deletions(-)

diff --git a/core/modules/datetime_range/tests/src/Functional/EntityResource/EntityTest/EntityTestDateRangeTest.php b/core/modules/datetime_range/tests/src/Functional/EntityResource/EntityTest/EntityTestDateRangeTest.php
index 6ed5bd0..22044f5 100644
--- a/core/modules/datetime_range/tests/src/Functional/EntityResource/EntityTest/EntityTestDateRangeTest.php
+++ b/core/modules/datetime_range/tests/src/Functional/EntityResource/EntityTest/EntityTestDateRangeTest.php
@@ -51,15 +51,13 @@ public function setUp() {
       'type' => 'daterange',
       'entity_type' => static::$entityTypeId,
       'settings' => ['datetime_type' => DateRangeItem::DATETIME_TYPE_ALLDAY],
-    ])
-      ->save();
+    ])->save();
 
     FieldConfig::create([
       'field_name' => static::$fieldName,
       'entity_type' => static::$entityTypeId,
       'bundle' => $this->entity->bundle(),
-    ])
-      ->save();
+    ])->save();
 
     // Reload entity so that it has the new field.
     $this->entity = $this->entityStorage->load($this->entity->id());
@@ -149,7 +147,7 @@ protected function assertNormalizationEdgeCases($method, Url $url, array $reques
       $message = "Unprocessable Entity: validation failed.\n{$fieldName}.0.end_value: This value should be of the correct primitive type.\n";
       $this->assertResourceErrorResponse(422, $message, $response);
 
-      // @todo Test more edge cases in https://www.drupal.org/project/drupal/issues/2847041.
+      // @todo Expand in https://www.drupal.org/project/drupal/issues/2847041.
     }
   }
 
diff --git a/core/modules/hal/src/Normalizer/TimestampItemNormalizer.php b/core/modules/hal/src/Normalizer/TimestampItemNormalizer.php
index 1d53099..476e7f5 100644
--- a/core/modules/hal/src/Normalizer/TimestampItemNormalizer.php
+++ b/core/modules/hal/src/Normalizer/TimestampItemNormalizer.php
@@ -11,7 +11,8 @@
  *
  * Overrides FieldItemNormalizer to
  * - during normalization, add the 'format' key to assist consumers
- * - during denormalization, use \Drupal\serialization\Normalizer\TimestampNormalizer
+ * - during denormalization, use
+ *   \Drupal\serialization\Normalizer\TimestampNormalizer
  */
 class TimestampItemNormalizer extends FieldItemNormalizer {
 
diff --git a/core/modules/serialization/src/Normalizer/DateTimeIso8601Normalizer.php b/core/modules/serialization/src/Normalizer/DateTimeIso8601Normalizer.php
index d579f96..de8143b 100644
--- a/core/modules/serialization/src/Normalizer/DateTimeIso8601Normalizer.php
+++ b/core/modules/serialization/src/Normalizer/DateTimeIso8601Normalizer.php
@@ -13,7 +13,7 @@
  *
  * @see \Drupal\datetime\Plugin\Field\FieldType\DateTimeItem::DATETIME_TYPE_DATE
  *
- * @todo Consider making "date only" a separate data type in Drupal 9.
+ * @todo Remove this in https://www.drupal.org/project/drupal/issues/2958416.
  */
 class DateTimeIso8601Normalizer extends DateTimeNormalizer {
 
@@ -55,7 +55,7 @@ public function denormalize($data, $class, $format = NULL, array $context = [])
     // @see \Drupal\datetime\Plugin\views\filter\Date::getOffset()
     // @see \Drupal\datetime\DateTimeComputed::getValue()
     $date->setTimezone(new \DateTimeZone('UTC'));
-    $date->setTime(0, 0, 0);
+    $date->setTime(12, 0, 0);
     return $date;
   }
 
diff --git a/core/modules/serialization/tests/src/Unit/Normalizer/DateTimeIso8601NormalizerTest.php b/core/modules/serialization/tests/src/Unit/Normalizer/DateTimeIso8601NormalizerTest.php
index 0a85f97..b5e6d1d 100644
--- a/core/modules/serialization/tests/src/Unit/Normalizer/DateTimeIso8601NormalizerTest.php
+++ b/core/modules/serialization/tests/src/Unit/Normalizer/DateTimeIso8601NormalizerTest.php
@@ -19,14 +19,13 @@
 /**
  * Unit test coverage for the "datetime_iso8601" @DataType.
  *
- * @group serialization
- * @coversDefaultClass \Drupal\serialization\Normalizer\DateTimeIso8601Normalizer
- * @see \Drupal\Core\TypedData\Plugin\DataType\DateTimeIso8601
- *
  * Only tests the "date only" mode of DateTimeIso8601, because everything else
  * is handled by \Drupal\serialization\Normalizer\DateTimeNormalizer, for which
  * we have \Drupal\Tests\serialization\Unit\Normalizer\DateTimeNormalizerTest.
  *
+ * @coversDefaultClass \Drupal\serialization\Normalizer\DateTimeIso8601Normalizer
+ * @group serialization
+ * @see \Drupal\Core\TypedData\Plugin\DataType\DateTimeIso8601
  * @see \Drupal\datetime\Plugin\Field\FieldType\DateTimeItem::DATETIME_TYPE_DATE
  */
 class DateTimeIso8601NormalizerTest extends UnitTestCase {
@@ -88,7 +87,7 @@ public function testSupportsDenormalization() {
 
   /**
    * @covers ::normalize
-   * @dataProvider testNormalizeProvider
+   * @dataProvider providerTestNormalize
    */
   public function testNormalize($parent_field_item_class, $datetime_type, $expected_format) {
     $formatted_string = $this->randomMachineName();
@@ -128,7 +127,7 @@ public function testNormalize($parent_field_item_class, $datetime_type, $expecte
    *
    * @return array
    */
-  public function testNormalizeProvider() {
+  public function providerTestNormalize() {
     return [
       // @see \Drupal\datetime\Plugin\Field\FieldType\DateTimeItem::DATETIME_TYPE_DATE
       'datetime field, configured to store only date: must be handled by DateTimeIso8601Normalizer' => [
@@ -173,7 +172,7 @@ public function testDenormalizeValidFormats($value, $expected) {
    */
   public function providerTestDenormalizeValidFormats() {
     $data = [];
-    $data["denormalized dates have the site's timezone"] = ['2016-11-06', new \DateTimeImmutable('2016-11-06T00:00:00+00:00')];
+    $data["denormalized dates have the site's timezone"] = ['2016-11-06', new \DateTimeImmutable('2016-11-06T12:00:00+00:00')];
     return $data;
   }