timestamp giver = 0

Jeg har en tabel:

CREATE TABLE db_userlog (
  id tinyint(4) DEFAULT \'0\' NOT NULL auto_increment,
  ip varchar(255) NOT NULL,
  host varchar(255) NOT NULL,
  dato timestamp(14),
  PRIMARY KEY (id)
);


og lidt phpkode:

<?
$ip = $REMOTE_ADDR;
$host = gethostbyaddr($ip);
#$host = $ip;

$time = explode(\" \",microtime());
$array1 = $time[0];
$array2 = $time[1];

    $r = mysql_fetch_row( mysql_query(\"SELECT * FROM db_userlog WHERE ip like \'$ip\'\"));
    if ($r == (false))  {
    mysql_query(\"INSERT INTO db_userlog (id,ip,host,dato) values (\'\',\'$ip\',\'\',\'$array2\')\");
    }
mysql_query(\"DELETE FROM db_userlog where dato < $array2 - 400\");
$res = mysql_query(\"SELECT * FROM db_userlog\");
$tal = mysql_num_rows($res);
if ($tal == \"1\") {
print \"1 bruger online \";
}
else {
print $tal;
print \" brugere online\";
}
?>

af en eller anden grund bliver \"dato\" i tabel\'en altid sat til 0 eller rettere 00000000000000.


Hvor går det galt ?