Index: modules/system/system.module
===================================================================
RCS file: /cvs/drupal/drupal/modules/system/system.module,v
retrieving revision 1.862
diff -u -p -r1.862 system.module
--- modules/system/system.module	15 Dec 2009 08:45:32 -0000	1.862
+++ modules/system/system.module	15 Dec 2009 17:23:17 -0000
@@ -3139,6 +3139,12 @@ function system_run_cron_check() {
       $cron_run = drupal_cron_run();
       // Release the cron threshold semaphore.
       variable_del('cron_threshold_semaphore');
+
+      if ($cron_run) {
+        // Truncate the page cache so that cached pages get a new timestamp for
+        // the next cron run.
+        cache_clear_all('*', 'cache_page', TRUE);
+      }
     }
   }