function dates_format($sdate, $edate)
{
    $syear = JDate::year($sdate);
    $eyear = JDate::year($edate);
    $ret = JDate::date_format($sdate, 'Y m月d日') . " ~ ";
    if ($syear == $eyear) {
        $ret .= JDate::date_format($edate, 'm月d日');
    } else {
        $ret .= JDate::date_format($edate, 'Y m月d日');
    }
    return $ret;
}