function testDate when,notBefore,notAfter
  put true into valid
  repeat with P = 1 to 8
    if char P of when is not in "/0123456789-" then put false into valid
  end repeat
  if valid then
    if notBefore is not empty and when < notBefore then put false into valid
    if notAfter is not empty and when > notAfter then put false into valid
  end if
  return valid
end testDate