Drupal Db_select and Date sql condition

Hi

Here is some code might be helpful for someone .. How we can use date condition in db_select

$query = db_select('file_managed', 'fm');
$query->leftJoin('field_data_field_video_upload', 'fd', 'fm.fid = fd.field_video_upload_fid');
$query->fields('fm', array('fid', 'filename'));
$query->where("FROM_UNIXTIME(fm.timestamp, '%Y%m%d') = :date", array(':date' => '20130430'));
$result = $query->execute()->fetchAll();
drupal_set_message("<pre>".print_r($result, true). "</pre>");   
  array_unshift($form['#validate'], 'vv_delete_node_change_field_values');