diff --git a/core/lib/Drupal/Core/Datetime/DrupalDateTime.php b/core/lib/Drupal/Core/Datetime/DrupalDateTime.php
index 572a6e3..27156e1 100644
--- a/core/lib/Drupal/Core/Datetime/DrupalDateTime.php
+++ b/core/lib/Drupal/Core/Datetime/DrupalDateTime.php
@@ -132,4 +132,17 @@ public function format($format, $settings = []) {
     return $value;
   }
 
+  /**
+   * Sets the default time for an object built from date-only data.
+   *
+   * The default time for a date without time can be anything, so long as it is
+   * consistently applied. If we use noon, dates in most timezones will have the
+   * same value for in both the local timezone and UTC.
+   *
+   * @param \Drupal\Core\Datetime\DrupalDateTime $date
+   */
+  public static function setDefaultDateTime(DrupalDateTime $date) {
+    $date->setTime(12, 0, 0);
+  }
+
 }
diff --git a/core/modules/datetime/datetime.module b/core/modules/datetime/datetime.module
index bb10d13..12c0f98 100644
--- a/core/modules/datetime/datetime.module
+++ b/core/modules/datetime/datetime.module
@@ -5,6 +5,7 @@
  * Field hooks to implement a simple datetime field.
  */
 
+use Drupal\Core\Datetime\DrupalDateTime;
 use Drupal\Core\Routing\RouteMatchInterface;
 
 /**
@@ -50,7 +51,11 @@ function datetime_help($route_name, RouteMatchInterface $route_match) {
  * same value for in both the local timezone and UTC.
  *
  * @param $date
+ *
+ * @deprecated in Drupal 8.4.0 and will be removed before Drupal 9.0.0. Use
+ *   \Drupal\Core\Datetime\DrupalDateTime::setDefaultDateTime() instead.
  */
 function datetime_date_default_time($date) {
-  $date->setTime(12, 0, 0);
+  @trigger_error('datetime_date_default_time() is deprecated in Drupal 8.4.0 and will be removed before Drupal 9.0.0. Use \Drupal\Core\Datetime\DrupalDateTime::setDefaultDateTime() instead.', E_USER_DEPRECATED);
+  DrupalDateTime::setDefaultDateTime($date);
 }
diff --git a/core/modules/datetime/src/DateTimeComputed.php b/core/modules/datetime/src/DateTimeComputed.php
index 9320baf..123d848 100644
--- a/core/modules/datetime/src/DateTimeComputed.php
+++ b/core/modules/datetime/src/DateTimeComputed.php
@@ -56,12 +56,10 @@ public function getValue($langcode = NULL) {
         // set the time to 12:00:00 UTC for date-only fields. This is used so
         // that the local date portion is the same, across nearly all time
         // zones.
-        // @see datetime_date_default_time()
+        // @see \Drupal\Core\Datetime\DrupalDateTime::setDefaultDateTime()
         // @see http://php.net/manual/en/datetime.createfromformat.php
-        // @todo Update comment and/or code per the chosen solution in
-        //   https://www.drupal.org/node/2830094
         if ($datetime_type === DateTimeItem::DATETIME_TYPE_DATE) {
-          $this->date->setTime(12, 0, 0);
+          DrupalDateTime::setDefaultDateTime($this->date);
         }
       }
     }
diff --git a/core/modules/datetime/src/Plugin/Field/FieldFormatter/DateTimeFormatterBase.php b/core/modules/datetime/src/Plugin/Field/FieldFormatter/DateTimeFormatterBase.php
index 71b9467..e623f13 100644
--- a/core/modules/datetime/src/Plugin/Field/FieldFormatter/DateTimeFormatterBase.php
+++ b/core/modules/datetime/src/Plugin/Field/FieldFormatter/DateTimeFormatterBase.php
@@ -202,10 +202,6 @@ protected function getFormatSettings() {
    *   A render array.
    */
   protected function buildDate(DrupalDateTime $date) {
-    if ($this->getFieldSetting('datetime_type') == DateTimeItem::DATETIME_TYPE_DATE) {
-      // A date without time will pick up the current time, use the default.
-      datetime_date_default_time($date);
-    }
     $this->setTimeZone($date);
 
     $build = [
@@ -230,11 +226,6 @@ protected function buildDate(DrupalDateTime $date) {
    *   A render array.
    */
   protected function buildDateWithIsoAttribute(DrupalDateTime $date) {
-    if ($this->getFieldSetting('datetime_type') == DateTimeItem::DATETIME_TYPE_DATE) {
-      // A date without time will pick up the current time, use the default.
-      datetime_date_default_time($date);
-    }
-
     // Create the ISO date in Universal Time.
     $iso_date = $date->format("Y-m-d\TH:i:s") . 'Z';
 
diff --git a/core/modules/datetime/src/Plugin/Field/FieldFormatter/DateTimeTimeAgoFormatter.php b/core/modules/datetime/src/Plugin/Field/FieldFormatter/DateTimeTimeAgoFormatter.php
index 3fc3157..782e1b8 100644
--- a/core/modules/datetime/src/Plugin/Field/FieldFormatter/DateTimeTimeAgoFormatter.php
+++ b/core/modules/datetime/src/Plugin/Field/FieldFormatter/DateTimeTimeAgoFormatter.php
@@ -110,10 +110,6 @@ public function viewElements(FieldItemListInterface $items, $langcode) {
       $date = $item->date;
       $output = [];
       if (!empty($item->date)) {
-        if ($this->getFieldSetting('datetime_type') == 'date') {
-          // A date without time will pick up the current time, use the default.
-          datetime_date_default_time($date);
-        }
         $output = $this->formatDate($date);
       }
       $elements[$delta] = $output;
diff --git a/core/modules/datetime/src/Plugin/Field/FieldWidget/DateTimeWidgetBase.php b/core/modules/datetime/src/Plugin/Field/FieldWidget/DateTimeWidgetBase.php
index f965e21..9d1fdcc 100644
--- a/core/modules/datetime/src/Plugin/Field/FieldWidget/DateTimeWidgetBase.php
+++ b/core/modules/datetime/src/Plugin/Field/FieldWidget/DateTimeWidgetBase.php
@@ -35,13 +35,8 @@ public function formElement(FieldItemListInterface $items, $delta, array $elemen
       $date = $items[$delta]->date;
       // The date was created and verified during field_load(), so it is safe to
       // use without further inspection.
-      if ($this->getFieldSetting('datetime_type') == DateTimeItem::DATETIME_TYPE_DATE) {
-        // A date without time will pick up the current time, use the default
-        // time.
-        datetime_date_default_time($date);
-      }
       $date->setTimezone(new \DateTimeZone($element['value']['#date_timezone']));
-      $element['value']['#default_value'] = $date;
+      $element['value']['#default_value'] = $this->createDefaultValue($date, $element['value']['#date_timezone']);
     }
 
     return $element;
@@ -59,9 +54,6 @@ public function massageFormValues(array $values, array $form, FormStateInterface
         $date = $item['value'];
         switch ($this->getFieldSetting('datetime_type')) {
           case DateTimeItem::DATETIME_TYPE_DATE:
-            // If this is a date-only field, set it to the default time so the
-            // timezone conversion can be reversed.
-            datetime_date_default_time($date);
             $format = DATETIME_DATE_STORAGE_FORMAT;
             break;
 
@@ -77,4 +69,28 @@ public function massageFormValues(array $values, array $form, FormStateInterface
     return $values;
   }
 
+  /**
+   * Creates a date object for use as a default value.
+   *
+   * This will take a default value, apply the proper timezone for display in
+   * a widget, and set the default time for date-only fields.
+   *
+   * @param \Drupal\Core\Datetime\DrupalDateTime $date
+   *   The UTC default date.
+   * @param string $timezone
+   *   The timezone to apply.
+   *
+   * @return \Drupal\Core\Datetime\DrupalDateTime
+   *   A date object for use as a default value in a field widget.
+   */
+  protected function createDefaultValue($date, $timezone) {
+    // The date was created and verified during field_load(), so it is safe to
+    // use without further inspection.
+    if ($this->getFieldSetting('datetime_type') === DateTimeItem::DATETIME_TYPE_DATE) {
+      DrupalDateTime::setDefaultDateTime($date);
+    }
+    $date->setTimezone(new \DateTimeZone($timezone));
+    return $date;
+  }
+
 }
diff --git a/core/modules/datetime/src/Tests/DateTestBase.php b/core/modules/datetime/src/Tests/DateTestBase.php
index a234ae0..ac1579b 100644
--- a/core/modules/datetime/src/Tests/DateTestBase.php
+++ b/core/modules/datetime/src/Tests/DateTestBase.php
@@ -5,6 +5,7 @@
 @trigger_error('\Drupal\datetime\Tests\DateTestBase is deprecated in Drupal 8.4.0 and will be removed before Drupal 9.0.0. Use \Drupal\Tests\BrowserTestBase instead. See https://www.drupal.org/node/2780063.', E_USER_DEPRECATED);
 
 use Drupal\Component\Utility\Unicode;
+use Drupal\Core\Datetime\DrupalDateTime;
 use Drupal\Core\Entity\Entity\EntityFormDisplay;
 use Drupal\Core\Entity\Entity\EntityViewDisplay;
 use Drupal\datetime\Plugin\Field\FieldType\DateTimeItem;
@@ -185,4 +186,20 @@ protected function setSiteTimezone($timezone) {
       ->save();
   }
 
+  /**
+   * Massages test date values.
+   *
+   * If a date object is generated directly by a test, then it needs to be
+   * adjusted to behave like the computed date from the item.
+   *
+   * @param \Drupal\Core\Datetime\DrupalDateTime $date
+   *   A date object directly generated by the test.
+   */
+  protected function massageTestDate($date) {
+    if ($this->field->getSetting('datetime_type') === DateTimeItem::DATETIME_TYPE_DATE) {
+      // Set the default time for date-only items.
+      DrupalDateTime::setDefaultDateTime($date);
+    }
+  }
+
 }
diff --git a/core/modules/datetime/tests/src/Functional/DateTestBase.php b/core/modules/datetime/tests/src/Functional/DateTestBase.php
index 369e793..c233951 100644
--- a/core/modules/datetime/tests/src/Functional/DateTestBase.php
+++ b/core/modules/datetime/tests/src/Functional/DateTestBase.php
@@ -3,6 +3,7 @@
 namespace Drupal\Tests\datetime\Functional;
 
 use Drupal\Component\Utility\Unicode;
+use Drupal\Core\Datetime\DrupalDateTime;
 use Drupal\Core\Entity\Entity\EntityFormDisplay;
 use Drupal\Core\Entity\Entity\EntityViewDisplay;
 use Drupal\datetime\Plugin\Field\FieldType\DateTimeItem;
@@ -181,4 +182,20 @@ protected function setSiteTimezone($timezone) {
       ->save();
   }
 
+  /**
+   * Massages test date values.
+   *
+   * If a date object is generated directly by a test, then it needs to be
+   * adjusted to behave like the computed date from the item.
+   *
+   * @param \Drupal\Core\Datetime\DrupalDateTime $date
+   *   A date object directly generated by the test.
+   */
+  protected function massageTestDate($date) {
+    if ($this->field->getSetting('datetime_type') === DateTimeItem::DATETIME_TYPE_DATE) {
+      // Set the default time for date-only items.
+      DrupalDateTime::setDefaultDateTime($date);
+    }
+  }
+
 }
diff --git a/core/modules/datetime/tests/src/Functional/DateTimeFieldTest.php b/core/modules/datetime/tests/src/Functional/DateTimeFieldTest.php
index ab03ff5..fcdf1fc 100644
--- a/core/modules/datetime/tests/src/Functional/DateTimeFieldTest.php
+++ b/core/modules/datetime/tests/src/Functional/DateTimeFieldTest.php
@@ -99,7 +99,7 @@ public function testDateField() {
       // Formats that display a time component for date-only fields will display
       // the default time, so that is applied before calculating the expected
       // value.
-      datetime_date_default_time($date);
+      $this->massageTestDate($date);
       foreach ($options as $setting => $values) {
         foreach ($values as $new_value) {
           // Update the entity display settings.
diff --git a/core/modules/datetime/tests/src/Kernel/DateTimeItemTest.php b/core/modules/datetime/tests/src/Kernel/DateTimeItemTest.php
index 9884007..5545aa5 100644
--- a/core/modules/datetime/tests/src/Kernel/DateTimeItemTest.php
+++ b/core/modules/datetime/tests/src/Kernel/DateTimeItemTest.php
@@ -2,6 +2,7 @@
 
 namespace Drupal\Tests\datetime\Kernel;
 
+use Drupal\Core\Datetime\DrupalDateTime;
 use Drupal\Core\Field\FieldItemListInterface;
 use Drupal\Core\Field\FieldItemInterface;
 use Drupal\datetime\Plugin\Field\FieldType\DateTimeItem;
@@ -122,22 +123,34 @@ public function testDateOnly() {
     $this->assertEqual($entity->field_datetime->value, $value);
     $this->assertEqual($entity->field_datetime[0]->value, $value);
     $this->assertEquals(DATETIME_STORAGE_TIMEZONE, $entity->field_datetime->date->getTimeZone()->getName());
+    $this->assertEquals('12:00:00', $entity->field_datetime->date->format('H:i:s'));
+    DrupalDateTime::setDefaultDateTime($entity->field_datetime->date);
+    $this->assertEquals('12:00:00', $entity->field_datetime->date->format('H:i:s'));
 
     // Verify changing the date value.
     $new_value = '2016-11-04';
     $entity->field_datetime->value = $new_value;
     $this->assertEqual($entity->field_datetime->value, $new_value);
     $this->assertEquals(DATETIME_STORAGE_TIMEZONE, $entity->field_datetime->date->getTimeZone()->getName());
+    $this->assertEquals('12:00:00', $entity->field_datetime->date->format('H:i:s'));
+    DrupalDateTime::setDefaultDateTime($entity->field_datetime->date);
+    $this->assertEquals('12:00:00', $entity->field_datetime->date->format('H:i:s'));
 
     // Read changed entity and assert changed values.
     $this->entityValidateAndSave($entity);
     $entity = EntityTest::load($id);
     $this->assertEqual($entity->field_datetime->value, $new_value);
     $this->assertEquals(DATETIME_STORAGE_TIMEZONE, $entity->field_datetime->date->getTimeZone()->getName());
+    $this->assertEquals('12:00:00', $entity->field_datetime->date->format('H:i:s'));
+    DrupalDateTime::setDefaultDateTime($entity->field_datetime->date);
+    $this->assertEquals('12:00:00', $entity->field_datetime->date->format('H:i:s'));
 
     // Test the generateSampleValue() method.
     $entity = EntityTest::create();
     $entity->field_datetime->generateSampleItems();
+    $this->assertEquals('12:00:00', $entity->field_datetime->date->format('H:i:s'));
+    DrupalDateTime::setDefaultDateTime($entity->field_datetime->date);
+    $this->assertEquals('12:00:00', $entity->field_datetime->date->format('H:i:s'));
     $this->entityValidateAndSave($entity);
   }
 
diff --git a/core/modules/datetime_range/src/Plugin/Field/FieldWidget/DateRangeWidgetBase.php b/core/modules/datetime_range/src/Plugin/Field/FieldWidget/DateRangeWidgetBase.php
index e99374c..b9238e8 100644
--- a/core/modules/datetime_range/src/Plugin/Field/FieldWidget/DateRangeWidgetBase.php
+++ b/core/modules/datetime_range/src/Plugin/Field/FieldWidget/DateRangeWidgetBase.php
@@ -58,9 +58,6 @@ public function massageFormValues(array $values, array $form, FormStateInterface
         $start_date = $item['value'];
         switch ($this->getFieldSetting('datetime_type')) {
           case DateRangeItem::DATETIME_TYPE_DATE:
-            // If this is a date-only field, set it to the default time so the
-            // timezone conversion can be reversed.
-            datetime_date_default_time($start_date);
             $format = DATETIME_DATE_STORAGE_FORMAT;
             break;
 
@@ -88,9 +85,6 @@ public function massageFormValues(array $values, array $form, FormStateInterface
         $end_date = $item['end_value'];
         switch ($this->getFieldSetting('datetime_type')) {
           case DateRangeItem::DATETIME_TYPE_DATE:
-            // If this is a date-only field, set it to the default time so the
-            // timezone conversion can be reversed.
-            datetime_date_default_time($end_date);
             $format = DATETIME_DATE_STORAGE_FORMAT;
             break;
 
@@ -142,30 +136,4 @@ public function validateStartEnd(array &$element, FormStateInterface $form_state
     }
   }
 
-  /**
-   * Creates a date object for use as a default value.
-   *
-   * This will take a default value, apply the proper timezone for display in
-   * a widget, and set the default time for date-only fields.
-   *
-   * @param \Drupal\Core\Datetime\DrupalDateTime $date
-   *   The UTC default date.
-   * @param string $timezone
-   *   The timezone to apply.
-   *
-   * @return \Drupal\Core\Datetime\DrupalDateTime
-   *   A date object for use as a default value in a field widget.
-   */
-  protected function createDefaultValue($date, $timezone) {
-    // The date was created and verified during field_load(), so it is safe to
-    // use without further inspection.
-    if ($this->getFieldSetting('datetime_type') == DateTimeItem::DATETIME_TYPE_DATE) {
-      // A date without time will pick up the current time, use the default
-      // time.
-      datetime_date_default_time($date);
-    }
-    $date->setTimezone(new \DateTimeZone($timezone));
-    return $date;
-  }
-
 }
diff --git a/core/modules/datetime_range/tests/src/Functional/DateRangeFieldTest.php b/core/modules/datetime_range/tests/src/Functional/DateRangeFieldTest.php
index 23ba8fa..ce6e22b 100644
--- a/core/modules/datetime_range/tests/src/Functional/DateRangeFieldTest.php
+++ b/core/modules/datetime_range/tests/src/Functional/DateRangeFieldTest.php
@@ -108,8 +108,8 @@ public function testDateRangeField() {
       // Formats that display a time component for date-only fields will display
       // the default time, so that is applied before calculating the expected
       // value.
-      datetime_date_default_time($start_date);
-      datetime_date_default_time($end_date);
+      $this->massageTestDate($start_date);
+      $this->massageTestDate($end_date);
 
       // Reset display options since these get changed below.
       $this->displayOptions = [
@@ -198,7 +198,7 @@ public function testDateRangeField() {
       $id = $match[1];
       $this->assertText(t('entity_test @id has been created.', ['@id' => $id]));
 
-      datetime_date_default_time($start_date);
+      $this->massageTestDate($start_date);
 
       $this->displayOptions = [
         'type' => 'daterange_default',
diff --git a/core/modules/datetime_range/tests/src/Kernel/DateRangeItemTest.php b/core/modules/datetime_range/tests/src/Kernel/DateRangeItemTest.php
index 67e1b9d..54f805f 100644
--- a/core/modules/datetime_range/tests/src/Kernel/DateRangeItemTest.php
+++ b/core/modules/datetime_range/tests/src/Kernel/DateRangeItemTest.php
@@ -100,6 +100,8 @@ public function testDateOnly() {
     sleep(1);
     $end_date = $entity->{$field_name}->end_date;
     $this->assertEquals($start_date->getTimestamp(), $end_date->getTimestamp());
+    $this->assertEquals('12:00:00', $start_date->format('H:i:s'));
+    $this->assertEquals('12:00:00', $end_date->format('H:i:s'));
   }
 
 }