core/modules/system/lib/Drupal/system/Entity/DateFormat.php | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/core/modules/system/lib/Drupal/system/Entity/DateFormat.php b/core/modules/system/lib/Drupal/system/Entity/DateFormat.php
index a3d6ece..320393f 100644
--- a/core/modules/system/lib/Drupal/system/Entity/DateFormat.php
+++ b/core/modules/system/lib/Drupal/system/Entity/DateFormat.php
@@ -9,6 +9,7 @@
 
 use Drupal\Core\Config\Entity\ConfigEntityBase;
 use Drupal\Core\Datetime\DrupalDateTime;
+use Drupal\Core\Entity\EntityStorageInterface;
 use Drupal\system\DateFormatInterface;
 
 /**
@@ -104,4 +105,16 @@ public function isLocked() {
     return (bool) $this->locked;
   }
 
+  /**
+   * {@inheritdoc}
+   */
+  public function postSave(EntityStorageInterface $storage, $update = TRUE) {
+    parent::postSave($storage, $update);
+
+    // Delete the entire render cache, because:
+    // - DateFormat entities are used all across Drupal core
+    // - DateFormat entities hardly ever change
+    \Drupal::cache('render')->deleteAll();
+  }
+
 }