diff --git a/core/modules/datetime/datetime.module b/core/modules/datetime/datetime.module
index 54365a6..1ebecbc 100644
--- a/core/modules/datetime/datetime.module
+++ b/core/modules/datetime/datetime.module
@@ -15,7 +15,7 @@
 /**
  * Defines the format that date and time should be stored in.
  */
-const DATETIME_DATETIME_STORAGE_FORMAT = 'Y-m-d\TH:i:s';
+const DATETIME_DATETIME_STORAGE_FORMAT = 'Y-m-d\TH:i:s+00:00';
 
 /**
  * Defines the format that dates should be stored in.
diff --git a/core/modules/datetime/src/DateTimeComputed.php b/core/modules/datetime/src/DateTimeComputed.php
index b4e7dc4..d9c490a 100644
--- a/core/modules/datetime/src/DateTimeComputed.php
+++ b/core/modules/datetime/src/DateTimeComputed.php
@@ -46,7 +46,15 @@ public function getValue($langcode = NULL) {
     $value = $item->{($this->definition->getSetting('date source'))};
 
     $datetime_type = $item->getFieldDefinition()->getSetting('datetime_type');
-    $storage_format = $datetime_type === DateTimeItem::DATETIME_TYPE_DATE ? DATETIME_DATE_STORAGE_FORMAT : DATETIME_DATETIME_STORAGE_FORMAT;
+    if ($item->getFieldDefinition()->getSetting('datetime_type') === 'date') {
+      $storage_format = DATETIME_DATE_STORAGE_FORMAT;
+    }
+    else {
+      // Strip off an explicit time from the format and replace with the
+      // time zone placeholder to allow the string to be parsed properly.
+      $storage_format = preg_replace('/\+\d\d\:\d\d$/', 'P', DATETIME_DATETIME_STORAGE_FORMAT);
+    }
+
     try {
       $date = DrupalDateTime::createFromFormat($storage_format, $value, DATETIME_STORAGE_TIMEZONE);
       if ($date instanceof DrupalDateTime && !$date->hasErrors()) {
diff --git a/core/modules/datetime/src/Plugin/Field/FieldFormatter/DateTimeFormatterBase.php b/core/modules/datetime/src/Plugin/Field/FieldFormatter/DateTimeFormatterBase.php
index 0891589..8ad7b82 100644
--- a/core/modules/datetime/src/Plugin/Field/FieldFormatter/DateTimeFormatterBase.php
+++ b/core/modules/datetime/src/Plugin/Field/FieldFormatter/DateTimeFormatterBase.php
@@ -226,7 +226,7 @@ protected function buildDate(DrupalDateTime $date) {
    */
   protected function buildDateWithIsoAttribute(DrupalDateTime $date) {
     // Create the ISO date in Universal Time.
-    $iso_date = $date->format("Y-m-d\TH:i:s") . 'Z';
+    $iso_date = $date->format("Y-m-d\TH:i:sP", ['timezone' => 'UTC']);
 
     $this->setTimeZone($date);
 
diff --git a/core/modules/datetime/src/Plugin/Field/FieldType/DateTimeItem.php b/core/modules/datetime/src/Plugin/Field/FieldType/DateTimeItem.php
index 330782b..1531e74 100644
--- a/core/modules/datetime/src/Plugin/Field/FieldType/DateTimeItem.php
+++ b/core/modules/datetime/src/Plugin/Field/FieldType/DateTimeItem.php
@@ -69,7 +69,7 @@ public static function schema(FieldStorageDefinitionInterface $field_definition)
         'value' => [
           'description' => 'The date value.',
           'type' => 'varchar',
-          'length' => 20,
+          'length' => 25,
         ],
       ],
       'indexes' => [