Workflow / Views: Specific state date
The Views PHP Module provides a custome field that is click sort enabled

Value code example:

....
$result = db_fetch_object(db_query("SELECT stamp FROM {workflow_node_history} WHERE nid = %d AND sid = %d", $row-&gt;nid, $sid));
if(isset($result-&gt;stamp)) {
   return $result-&gt;stamp;
}
return 0;


Output code:

&lt;?php 
print date('d.m.Y', $value);
?&gt;


Enable click sort: sort numerically