diff -u b/core/modules/system/lib/Drupal/system/Tests/System/DateTimeTest.php b/core/modules/system/lib/Drupal/system/Tests/System/DateTimeTest.php
--- b/core/modules/system/lib/Drupal/system/Tests/System/DateTimeTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/System/DateTimeTest.php
@@ -62,7 +62,7 @@
     $this->assertText('2007-07-31 21:00:00 -1000', 'Date should be identical, with GMT offset of -10 hours.');
 
     // Set time zone to Los Angeles time.
-    $config->set('default', 'America/Los_Angeles')->save();
+    $config->set('timezone.default', 'America/Los_Angeles')->save();
 
     // Confirm date format and time zone.
     $this->drupalGet("node/$node1->nid");
only in patch2:
unchanged:
--- a/core/lib/Drupal/Core/Config/Context/ConfigContext.php
+++ b/core/lib/Drupal/Core/Config/Context/ConfigContext.php
@@ -63,6 +63,8 @@ public function __construct(EventDispatcher $event_dispatcher) {
    * Implements Drupal\Core\Config\Context\ContextInterface::init().
    */
   public function init() {
+    // Reset and existing overrides and get a UUID for this context.
+    $this->overrides = array();
     $this->setUuid();
     // Notify event listeners that a configuration context has been created.
     $this->notify('context', NULL);
only in patch2:
unchanged:
--- a/core/modules/locale/lib/Drupal/locale/LocaleConfigSubscriber.php
+++ b/core/modules/locale/lib/Drupal/locale/LocaleConfigSubscriber.php
@@ -87,6 +87,11 @@ public function configLoad(ConfigEvent $event) {
   public function onKernelRequestSetDefaultConfigContextLocale(GetResponseEvent $event) {
     if ($language = $this->languageManager->getLanguage(LANGUAGE_TYPE_INTERFACE)) {
       $this->defaultConfigContext->set('locale.language', $language);
+      // Re-initialize the default configuration context to ensure any cached
+      // configuration object are reset and can be translated. This will invoke
+      // the config context event which will retrieve the negotiated language
+      // from the language manager in configContext().
+      $this->defaultConfigContext->init();
     }
   }