Menu callback; present a form for deleting a date format.
function system_date_delete_format_form($form, &$form_state, $dfid) {
$form['dfid'] = array(
'#type' => 'value',
'#value' => $dfid,
);
$format = system_get_date_format($dfid);
$output = confirm_form($form, t('Are you sure you want to remove the format %format?', array(
'%format' => format_date(REQUEST_TIME, 'custom', $format->format),
)), 'admin/config/regional/date-time/formats', t('This action cannot be undone.'), t('Remove'), t('Cancel'), 'confirm');
return $output;
}