it maybe wrong,
since the parameter "timestamp" of date is a UNIX timestamp, the number of seconds since the Unix Epoch (January 1 1970 00:00:00 GMT). But Mysql timestamp is in format like YYYYMMDDHHIISS, which is difference form UNIX timestamp.
so should do this:
$year = substr($mysql_timestamp, 0, 4);
$month = substr($mysql_timestamp, 4, 2);
$day = substr($mysql_timestamp, 6, 2);
$hour = substr($mysql_timestamp, 8, 2);
$min = substr($mysql_timestamp, 10, 2);
$sec = substr($mysql_timestamp, 12, 14);
$new_date = data("Y-m-d H:i:s", mktime($hour, $min, $sec, $month, $day, $year ));
correct me if i'm wrong