Alter node before render or after save
hook_node_presave() can help you making the changes


  Act on a node being inserted or updated. This hook is invoked from node_save() before the node is saved to the
  database.


so inside this hook you can get the created time and can change the title.

As an example code: Here I am making node title as the time article node is created.

function mymodulename_node_presave($node) {
  if($node-&gt;type == "article") {
    $node-&gt;title = $node-&gt;created;
  }
}


Make sure you do not call node_save() inside this function, else this will turn out to non breking recursion.