Drupal 8.0.0 beta 12. More info: https://www.drupal.org/node/2514176

core/modules/update/templates/update-last-check.html.twig

@@ -0,0 +1,23 @@
+{#
+/**
+ * @file
+ * Default theme implementation for the last time update data was checked.
+ *
+ * Available variables:
+ * - last: The timestamp that the site was last checked for updates.
+ * - time: The formatted time since the site last checked for updates.
+ * - link: A link to check for updates manually.
+ *
+ * @see template_preprocess_update_last_check()
+ *
+ * @ingroup themeable
+ */
+#}
+<p>
+  {% if last %}
+    {{ 'Last checked: @time ago'|t({'@time': time}) }}
+  {% else %}
+    {{ 'Last checked: never'|t }}
+  {% endif %}
+  ({{ link }})
+</p>