Index: scripts/arcanist.php
===================================================================
--- scripts/arcanist.php
+++ scripts/arcanist.php
@@ -61,7 +61,7 @@
 $workflow = null;
 
 try {
-
+  check_arcanist_age($console);
   $console->writeLog(
     "libphutil loaded from '%s'.\n",
     phutil_get_library_root('phutil'));
@@ -552,6 +552,15 @@
   }
 }
 
+function check_arcanist_age(PhutilConsole $console) {
+  // Todo: skip if running 'arc upgrade'
+  $arc_dir = dirname(__DIR__);
+  $date = (int) `cd $arc_dir && git log -1 --format=%ct && cd -`;
+  if ($date < time() - (86400 * 30)) {
+    $console->writeOut("<fg:yellow>**Arcanist is more than 30 days out of date."
+    ." You should run 'arc upgrade'.**</fg>\n");
+  }
+}
 
 /**
  * NOTE: SPOOKY BLACK MAGIC