alias isdate {
  if $count($1,/) > 2 return 0
  tokenize 47 $1
  return $iif(. isin $1- || $1 !isnum 1-31 || $2 !isnum 1-12 || !$3 || ($2 = 2 && ($1 > 29 || ($1 = 29 && (4 \\ $3 || 100 // $3 && 400 \\ $3)))) || ($right($2,2) !isin 030507081012 && $1 = 31),0,1)