diff --git a/core/modules/datetime/datetime.module b/core/modules/datetime/datetime.module
index bb10d13..22109be 100644
--- a/core/modules/datetime/datetime.module
+++ b/core/modules/datetime/datetime.module
@@ -50,6 +50,9 @@ function datetime_help($route_name, RouteMatchInterface $route_match) {
  * same value for in both the local timezone and UTC.
  *
  * @param $date
+ *
+ * @deprecated in Drupal 8.4.0 and will be removed before Drupal 9.0.0. Use
+ *   (TBD) instead.
  */
 function datetime_date_default_time($date) {
   $date->setTime(12, 0, 0);
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..7514ae8 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) {
+      $date->setTime(12, 0, 0);
+    }
+    $date->setTimezone(new \DateTimeZone($timezone));
+    return $date;
+  }
+
 }
diff --git a/core/modules/datetime/src/Tests/DateTestBase.php b/core/modules/datetime/src/Tests/DateTestBase.php
index a234ae0..5c476a0 100644
--- a/core/modules/datetime/src/Tests/DateTestBase.php
+++ b/core/modules/datetime/src/Tests/DateTestBase.php
@@ -185,4 +185,21 @@ protected function setSiteTimezone($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) {
+      // Mirror what \Drupal\datetime\DateTimeComputed::getValue() does to
+      // date-only items.
+      $date->setTime(12, 0, 0);
+    }
+  }
+
 }
diff --git a/core/modules/datetime/tests/src/Functional/DateTimeFieldTest.php b/core/modules/datetime/tests/src/Functional/DateTimeFieldTest.php
index ab03ff5..fcdf1fc 100644
--- a/core/modules/datetime/tests/src/Functional/DateTimeFieldTest.php
+++ b/core/modules/datetime/tests/src/Functional/DateTimeFieldTest.php
@@ -99,7 +99,7 @@ public function testDateField() {
       // Formats that display a time component for date-only fields will display
       // the default time, so that is applied before calculating the expected
       // value.
-      datetime_date_default_time($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_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',