When i create milestone i see that due date is required field, but when i click save button i see error with milestone name only and if i leave due date field is blank my milestone will be succesfully created
i fined this code in \application\models\project_milestones\ProjectMilestone.class.php
function validate(&$errors) {
if(!$this->getObject()->validatePresenceOf('name')) $errors[] = lang('milestone name required');
if(!$this->validatePresenceOf('due_date')) $errors[] = lang('milestone due date required');
} // validate
maybe this option can be activated in admininstration panel?