How can I edit all nodes of thier dates at once?
In this case, you could update the field in the db, much faster than node_loading and saving all the nodes with batch update etc.. backup db first.

Fields are:

node.created
node.changed
node_revision.timestamp (same as node changed)


e.g

$created = strtotime('2013-01-01 00:00:00');
$changed = REQUEST_TIME; // now

$query = db_update('node');
$query-&gt;fields(array('created' =&gt; $created, 'changed' =&gt; $changed));
$updated = $query-&gt;execute();

$query = db_update('node_revision');
$query-&gt;fields(array('timestamp' =&gt; $changed));
$updated = $query-&gt;execute();

drupal_flush_all_caches(); // clear cache