that would be nice, but for now:
Code:
on *:JOIN:#:{
  hadd -m $chan $nick $ticks
}
on *:PART:#:{
  if ($nick == $me) { hfree $chan }
  else { hdel $chan $nick }
}
on *:QUIT:{
  var %i $comchan($nick,0)
  while (%i) {
    hdel $comchan($nick,%i) $nick
    dec %i
  }
}
on *:NICK:{
  var %i $comchan($newnick,0)
  while (%i) {
    hadd -m $comchan($newnick,%i) $newnick $hget($comchan($newnick,%i),$nick)
    hdel $comchan($newnick,%i) $nick
    dec %i
  }
}
alias joined {
  return $calc(($ticks - $hget($1,$2)) / 1000)
}

//echo -a $joined(<chan>,<nick>)

new username: tidy_trax