rrrr-mm-dd

function isValidDate(subject){
  if (subject.match(/^(19|20)[0-9]{2})$/)[\- \/.](?:(0[1-9]|1[012])[\- \/.](0[1-9]|[12][0-9]|3[01])){
    return true;
  }else{
    return false;
  }
}