/*  http://paulschreiber.com/blog/2007/03/02/javascript-date-validation/ */

String.prototype.isValidDate = function() {
  var IsoDateRe = new RegExp("^([0-9]{4})-([0-9]{2})-([0-9]{2})$");

  var matches = IsoDateRe.exec(this);
  if (!matches) return false;

  var composedDate = new Date(matches[1], (matches[2] - 1), matches[3]);

  return ((composedDate.getMonth() == (matches[2] - 1)) &&
          (composedDate.getDate() == matches[3]) &&
          (composedDate.getFullYear() == matches[1]));
}