diff --git a/core/modules/datetime/datetime.module b/core/modules/datetime/datetime.module
index 245d0c4..a925706 100644
--- a/core/modules/datetime/datetime.module
+++ b/core/modules/datetime/datetime.module
@@ -27,7 +27,7 @@
  *
  * @see https://www.drupal.org/node/2912980
  */
-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 16f664b..d6f5e5a 100644
--- a/core/modules/datetime/src/DateTimeComputed.php
+++ b/core/modules/datetime/src/DateTimeComputed.php
@@ -47,7 +47,15 @@ public function getValue() {
     $value = $item->{($this->definition->getSetting('date source'))};
 
     $datetime_type = $item->getFieldDefinition()->getSetting('datetime_type');
-    $storage_format = $datetime_type === DateTimeItem::DATETIME_TYPE_DATE ? DateTimeItemInterface::DATE_STORAGE_FORMAT : DateTimeItemInterface::DATETIME_STORAGE_FORMAT;
+    if ($item->getFieldDefinition()->getSetting('datetime_type') === 'date') {
+      $storage_format = DateTimeItemInterface::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', DateTimeItemInterface::DATETIME_STORAGE_FORMAT);
+    }
+
     try {
       $date = DrupalDateTime::createFromFormat($storage_format, $value, DateTimeItemInterface::STORAGE_TIMEZONE);
       if ($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 a6680f6..1d41688 100644
--- a/core/modules/datetime/src/Plugin/Field/FieldFormatter/DateTimeFormatterBase.php
+++ b/core/modules/datetime/src/Plugin/Field/FieldFormatter/DateTimeFormatterBase.php
@@ -227,7 +227,7 @@ 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 3264069..6528192 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' => [
diff --git a/core/modules/datetime/src/Plugin/Field/FieldType/DateTimeItemInterface.php b/core/modules/datetime/src/Plugin/Field/FieldType/DateTimeItemInterface.php
index a9231c6..7171233 100644
--- a/core/modules/datetime/src/Plugin/Field/FieldType/DateTimeItemInterface.php
+++ b/core/modules/datetime/src/Plugin/Field/FieldType/DateTimeItemInterface.php
@@ -15,7 +15,7 @@
   /**
    * Defines the format that date and time should be stored in.
    */
-  const DATETIME_STORAGE_FORMAT = 'Y-m-d\TH:i:s';
+  const DATETIME_STORAGE_FORMAT = 'Y-m-d\TH:i:s+00:00';
 
   /**
    * Defines the format that dates should be stored in.