diff --git a/src/Drupal/Driver/Fields/Drupal8/DatetimeHandler.php b/src/Drupal/Driver/Fields/Drupal8/DatetimeHandler.php
index 006db8fc..2b17f1c9 100644
--- a/src/Drupal/Driver/Fields/Drupal8/DatetimeHandler.php
+++ b/src/Drupal/Driver/Fields/Drupal8/DatetimeHandler.php
@@ -2,6 +2,9 @@
 
 namespace Drupal\Driver\Fields\Drupal8;
 
+use DateTime;
+use DateTimeZone;
+
 /**
  * Datetime field handler for Drupal 8.
  */
@@ -11,6 +14,8 @@ class DatetimeHandler extends AbstractHandler {
    * {@inheritdoc}
    */
   public function expand($values) {
+    $siteTimezone = new DateTimeZone(\Drupal::config('system.date')->get('timezone.default'));
+    $storageTimezone = new DateTimeZone(DATETIME_STORAGE_TIMEZONE);
     foreach ($values as $key => $value) {
       if (strpos($value, "relative:") !== FALSE) {
         $relative = trim(str_replace('relative:', '', $value));
@@ -18,7 +23,13 @@ public function expand($values) {
         $values[$key] = substr(gmdate('c', strtotime($relative)), 0, 19);
       }
       else {
-        $values[$key] = str_replace(' ', 'T', $value);
+        // A Drupal install has a default site timezone, but nonetheless
+        // uses UTC for internal storage. If no timezone is specified in a date
+        // field value by the step author, assume the default timezone of
+        // the Drupal install, and therefore transform it into UTC for storage.
+        $date = new DateTime($value, $siteTimezone);
+        $date->setTimezone($storageTimezone);
+        $values[$key] = $date->format('Y-m-d\TH:i:s');
       }
     }
     return $values;