//the most obvious sulution is substr().
$timestamp = "20020321163021";
echo substr($timestamp,0,4).'/'.substr($timestamp,4,2).'/'.substr($timestamp,6,2).' '.substr($timestamp,8,2).':'.substr($timestamp,10,2);
// BUT... Here's a better solution:
//You could use mktime()...
$time = mktime (substr($timestamp,8,2), substr($timestamp,10,2), substr($timestamp,12,2), substr($timestamp,4,2), substr($timestamp,6,2), substr($timestamp,0,4));
//...and then use date() to print it out in ANY format!
// see http://us2.php.net/manual/en/function.date.php for more info.
date("Y/m/d H:i", $time);