WHERE date > CURDATE()
. Для истекших записей соответственно WHERE date < CURDATE()
. Ну на край можно столбец isEnded добавить <?php
include("bd.php");
$res=mysql_query("SELECT * FROM `messages` WHERE `id_add` = '". $_COOKIE['doc_id'] . "' AND `id_to` = '". $_COOKIE['user_id'] . "' AND `id_add_pac` = '". $_COOKIE['user_id'] . "' AND `id_to_pac` = '". $_COOKIE['doc_id'] . "' ORDER BY `id`");
while($d=mysql_fetch_array($res))
{
echo "<b><font color='white'>".$d['login'].": </font></b>".$d['message']."<br>";
}
?>