function hms2sec ($hms) {
	list($h, $m, $s) = explode (":", $hms);
	$seconds = 0;
	$seconds += (intval($h) * 3600);
	$seconds += (intval($m) * 60);
	$seconds += (intval($s));
	return $seconds;
}
$zaman= '17:17:34';
$gun=17;
$toplamSaniye = hms2sec($zaman);
$saniye= $toplamSaniye/$gun;
$kalan= gmdate("H:i:s", $saniye);
echo $kalan;