diff --git a/core/modules/serialization/src/Normalizer/DateTimeIso8601Normalizer.php b/core/modules/serialization/src/Normalizer/DateTimeIso8601Normalizer.php
index de8143bc56..6367762c8c 100644
--- a/core/modules/serialization/src/Normalizer/DateTimeIso8601Normalizer.php
+++ b/core/modules/serialization/src/Normalizer/DateTimeIso8601Normalizer.php
@@ -50,13 +50,19 @@ public function normalize($datetime, $format = NULL, array $context = []) {
    */
   public function denormalize($data, $class, $format = NULL, array $context = []) {
     $date = parent::denormalize($data, $class, $format, $context);
-    // For consistency, we set the time to 12:00:00 UTC for date-only fields.
+    // Extract the year, month, and day from the object.
+    $ymd = $date->format('Y-m-d');
+    // Rebuild the date object using the extracted year, month, and day, but
+    // for consistency set the time to 12:00:00 UTC upon creation for date-only
+    // fields. Rebuilding, instead of using the object methods, is done to
+    // avoid the initial date object picking up the local time and time zone
+    // from an input value with a missing or partial time string, and then
+    // rolling over to a different day when changing the object to UTC.
     // @see \Drupal\Component\Datetime\DateTimePlus::setDefaultDateTime()
     // @see \Drupal\datetime\Plugin\views\filter\Date::getOffset()
     // @see \Drupal\datetime\DateTimeComputed::getValue()
-    $date->setTimezone(new \DateTimeZone('UTC'));
-    $date->setTime(12, 0, 0);
-    return $date;
+    // @see http://php.net/manual/en/datetime.createfromformat.php
+    return \DateTime::createFromFormat('Y-m-d\TH:i:s O', $ymd . 'T12:00:00 UTC');
   }
 
 }
diff --git a/core/modules/serialization/tests/src/Unit/Normalizer/DateTimeIso8601NormalizerTest.php b/core/modules/serialization/tests/src/Unit/Normalizer/DateTimeIso8601NormalizerTest.php
index c269ce9c7b..f49a47e8fb 100644
--- a/core/modules/serialization/tests/src/Unit/Normalizer/DateTimeIso8601NormalizerTest.php
+++ b/core/modules/serialization/tests/src/Unit/Normalizer/DateTimeIso8601NormalizerTest.php
@@ -161,9 +161,10 @@ public function testDenormalizeValidFormats($value, $expected) {
     $normalized = ['value' => $value];
 
     $denormalized = $this->normalizer->denormalize($normalized, DateTimeIso8601::class, NULL, []);
-    $this->assertEquals($expected->format(\DateTime::RFC3339), $denormalized->format(\DateTime::RFC3339));
+    $this->assertInstanceOf(\DateTime::class, $denormalized);
     $this->assertEquals('UTC', $denormalized->getTimezone()->getName());
     $this->assertEquals('12:00:00', $denormalized->format('H:i:s'));
+    $this->assertEquals($expected->format(\DateTime::RFC3339), $denormalized->format(\DateTime::RFC3339));
   }
 
   /**