timestamp not working

[bitphire]

I know there is a lot of stuff on this but i cant figure it out. All that shows in my db is a bunch of 00000000000 and i am not sure why. DB is setup as

username varchar(20), password varchar(10), joined timestamp

EDIT:
tried switching timestamp to datetime but all i see now is 0000-00-00 00:00:00

then here is the code:

	include 'db_connect.php';

$username = $_POST['username'];
$password = $_POST['password'];
$joined = date("m.d.y h:i:s A");

echo $username . "<br />" . $password . "<br />" . $today . "<br />" . $time . "<br />";

$query = "INSERT INTO members (Username, Password, Joined) VALUES ('$username','$password','$joined')";

mysql_query($query)
	or die('User could not be added! ' . mysql_error());

[planetsim]

Notice the format of the DATETIME

0000-00-00 00:00:00 
YYYY-MM-DD HH:II:SS

Try chaning your $joined to this

$joined = date("Y-m-d h:i:s");

Also if your going to use timestamp as the field type use time() function or use the MySQL Function NOW()