silverstripe-framework/tasks/MonthlyTask.php

<?php
/**
 * Classes that must be run monthly extend this class
 * 
 * Please note: Subclasses of this task aren't extecuted automatically,
 * they need to be triggered by an external automation tool like unix cron.
 * See {@link ScheduledTask} for details.
 * 
 * @package sapphire
 * @subpackage cron
 */
class MonthlyTask extends ScheduledTask {

}