By default, SPIP orders articles by their publishing date (the SQL field date) from the most recent to the oldest.
It is possible to define this constant in your config/mes_options.php file (refer to the article dedicated to The mes_options.php file).
Example:
// sort the articles in the private zone on the modification
// date, showing the most recent modified first down to the
// least recently modified
define('_TRI_ARTICLES_RUBRIQUE', 'date_modif DESC');