diff --git a/core/modules/datetime/src/DateTimeComputed.php b/core/modules/datetime/src/DateTimeComputed.php
index 6939994..b6a1212 100644
--- a/core/modules/datetime/src/DateTimeComputed.php
+++ b/core/modules/datetime/src/DateTimeComputed.php
@@ -43,7 +43,16 @@ public function getValue($langcode = NULL) {
     $item = $this->getParent();
     $value = $item->{($this->definition->getSetting('date source'))};
 
-    $storage_format = $item->getFieldDefinition()->getSetting('datetime_type') == 'date' ? DATETIME_DATE_STORAGE_FORMAT : DATETIME_DATETIME_STORAGE_FORMAT;
+    if ($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 = DATETIME_DATETIME_STORAGE_FORMAT;
+      $storage_format = preg_replace('/\+\d\d\:\d\d$/', 'P', $storage_format);
+    }
+
     try {
       $date = DrupalDateTime::createFromFormat($storage_format, $value, DATETIME_STORAGE_TIMEZONE);
       if ($date instanceof DrupalDateTime && !$date->hasErrors()) {