commit b945e9994a48d8edc7e350f5f7d3519ce16f8902
Author: Dean Reilly <dean.reilly@gmail.com>
Date:   Sat Sep 29 18:02:45 2012 +0100

    Included install_time variable and added update hook.

diff --git a/core/includes/install.core.inc b/core/includes/install.core.inc
index 3046b87..bcdb1b9 100644
--- a/core/includes/install.core.inc
+++ b/core/includes/install.core.inc
@@ -1994,5 +1994,5 @@ function install_configure_form_submit($form, &$form_state) {
   user_login_finalize();
 
   // Record when this install ran.
-  variable_set('install_time', $_SERVER['REQUEST_TIME']);
+  state()->set('install_time', $_SERVER['REQUEST_TIME']);
 }
diff --git a/core/modules/system/system.install b/core/modules/system/system.install
index 0e3d3d6..be03ab6 100644
--- a/core/modules/system/system.install
+++ b/core/modules/system/system.install
@@ -274,7 +274,7 @@ function system_requirements($phase) {
     // Determine when cron last ran.
     $cron_last = variable_get('cron_last');
     if (!is_numeric($cron_last)) {
-      $cron_last = variable_get('install_time', 0);
+      $cron_last = state()->get('install_time') ?: 0;
     }
 
     // Determine severity based on time since cron last ran.
@@ -1976,13 +1976,17 @@ function system_update_8021() {
 }
 
 /**
- * Convert install_task variable to state api value.
+ * Convert install_task and install_time variables to state api values.
  */
 function system_update_8022() {
-  if ($install_task = update_variable_get('install_task', FALSE)) {
-    state()->set('install_task', $install_task);
+  $variables = array('install_task', 'install_time');
+
+  foreach ($variables as $variable) {
+    if ($value = update_variable_get($variable, FALSE)) {
+      state()->set($variable, $value);
+    }
+    update_variable_del($variable);
   }
-  update_variable_del('install_task');
 }
 
 /**