diff --git a/core/lib/Drupal/Core/Datetime/Element/Datetime.php b/core/lib/Drupal/Core/Datetime/Element/Datetime.php
index eaf9df1..51a2b08 100644
--- a/core/lib/Drupal/Core/Datetime/Element/Datetime.php
+++ b/core/lib/Drupal/Core/Datetime/Element/Datetime.php
@@ -97,6 +97,7 @@ public static function valueCallback(&$element, $input, FormStateInterface $form
       $input = array(
         'date'   => $date_input,
         'time'   => $time_input,
+        'timezone' => $timezone,
         'object' => $date,
       );
     }
diff --git a/core/modules/datetime/src/Plugin/Field/FieldType/DateTimeItem.php b/core/modules/datetime/src/Plugin/Field/FieldType/DateTimeItem.php
index 1727fd3..5fa252b 100644
--- a/core/modules/datetime/src/Plugin/Field/FieldType/DateTimeItem.php
+++ b/core/modules/datetime/src/Plugin/Field/FieldType/DateTimeItem.php
@@ -103,7 +103,8 @@ public static function schema(FieldStorageDefinitionInterface $field_definition)
         ),
       ),
       'indexes' => array(
-        'value' => array('value', 'timezone'),
+        'value' => array('value'),
+        'value_timezone' => array('value', 'timezone'),
       ),
     );
 
@@ -132,10 +133,10 @@ public function storageSettingsForm(array &$form, FormStateInterface $form_state
       '#type' => 'select',
       '#title' => t('Timezone handling'),
       '#options' => array(
-        static::TIMEZONE_SITE => t("Site's timezone"),
-        static::TIMEZONE_DATE => t("Date's timezone"),
-        static::TIMEZONE_USER => t("User's timezone"),
-        static::TIMEZONE_NONE => t('No timezone conversion'),
+        static::TIMEZONE_SITE => $this->t("Site's timezone"),
+        static::TIMEZONE_DATE => $this->t("Date's timezone"),
+        static::TIMEZONE_USER => $this->t("User's timezone"),
+        static::TIMEZONE_NONE => $this->t('No timezone conversion'),
       ),
       '#default_value' => $this->getSetting('timezone_handling'),
       '#required' => TRUE,
diff --git a/core/modules/datetime/src/Plugin/Field/FieldWidget/DateTimeWidgetBase.php b/core/modules/datetime/src/Plugin/Field/FieldWidget/DateTimeWidgetBase.php
index f2b217f0..65326f2 100644
--- a/core/modules/datetime/src/Plugin/Field/FieldWidget/DateTimeWidgetBase.php
+++ b/core/modules/datetime/src/Plugin/Field/FieldWidget/DateTimeWidgetBase.php
@@ -56,7 +56,6 @@ public function formElement(FieldItemListInterface $items, $delta, array $elemen
       }
       $date->setTimezone(new \DateTimeZone($element['value']['#date_timezone']));
       $element['value']['#default_value'] = $date;
-      $element['timezone']['#default_value'] = $date->format('e');
     }
 
     return $element;
@@ -93,8 +92,11 @@ public function massageFormValues(array $values, array $form, FormStateInterface
           $item['timezone'] = '';
         }
 
-        // Adjust the date for storage.
-        $date->setTimezone(new \DateTimezone(DATETIME_STORAGE_TIMEZONE));
+        // Adjust the date for storage once validation is complete.
+        if ($form_state->isValidationComplete()) {
+          $date->setTimezone(new \DateTimezone(DATETIME_STORAGE_TIMEZONE));
+        }
+
         $item['value'] = $date->format($format);
       }
     }
diff --git a/core/modules/datetime/src/Tests/DateTimeFieldTest.php b/core/modules/datetime/src/Tests/DateTimeFieldTest.php
index 19868d6..b7984f1 100644
--- a/core/modules/datetime/src/Tests/DateTimeFieldTest.php
+++ b/core/modules/datetime/src/Tests/DateTimeFieldTest.php
@@ -431,8 +431,8 @@ function testDatetimeField() {
     $this->fieldStorage->save();
 
     $edit = array(
-      "{$field_name}[0][value][date]" => $date->format($date_format),
-      "{$field_name}[0][value][time]" => $date->format($time_format),
+      "{$field_name}[0][value][date]" => $date->format($date_format, ['timezone' => 'America/New_York']),
+      "{$field_name}[0][value][time]" => $date->format($time_format, ['timezone' => 'America/New_York']),
       "{$field_name}[0][value][timezone]" => 'America/New_York',
     );
     $this->drupalPostForm('entity_test/add', $edit, t('Save'));