alias isdate {
  var %a,%x = return
  tokenize 47 $1
  scon -r if ( $* isnum) $(&&) (. !isin $* ) inc $(%a,)
  if %a != 3 || if $left($3,1) = 0 || $len($3) != 4 || !$x($1,d) || (!$x($2)) %x 0
  %a = 31 $iif(. isin $calc($3 /400),28,29) 31 30 31 30 31 31 30 31 30 31
  if $istok(29 30 31,$1,32) && ($1 != $gettok(%a,$base($2,10,10,1),32)) %x 0
  %x 1
}
alias x if $iif($left($1,1) = 0,$base($1,10,10,1),$1) isnum $iif($2,1-31,1-12) return 1