use DBI qw(:sql_types);    # make sure DBI gives you access to sql_types strings

$Array[0] = undef;
$sth = $dbh->prepare("INSERT into MYTABLE (mydate) VALUES(?)");
$sth->bind_param( 1, $Array[0], SQL_DATETIME );   # forces the data type
$sth->execute;   # no args needed here now.