Delete a configured date format.
function system_date_delete_format_form_submit($form, &$form_state) {
if ($form_state['values']['confirm']) {
$format = system_get_date_formats($form_state['values']['date_format_id']);
system_date_format_delete($form_state['values']['date_format_id']);
drupal_set_message(t('Removed date format %format.', array(
'%format' => $format['name'],
)));
$form_state['redirect'] = 'admin/config/regional/date-time/formats';
}
}