$sql = "SELECT * FROM {$modx->getTableName('modResource')} WHERE `editedon` < ".strtotime('2000-02-24 00:00:00')." LIMIT 1000";
$q = new xPDOCriteria($modx, $sql);
$docs = $modx->getCollection('modResource', $q);
 
echo '<pre>';
$i=1;
foreach($docs as $doc){
 
    $dat = $doc->get('editedon');
    $content = $doc->get('pagetitle');
    echo $i.'  '.$content.'  '.$dat.'  '.strtotime($dat);
    echo "\n";
 
    $i=$i+1;
    //$doc->set('editedon','2017-02-23 00:00:00');
    //$doc->save();
}
echo '</pre>';