JavaScript: Date validator

gistfile1.js

function isValidDate(date) {
      var matches = /^(\d{2})[-\/](\d{2})[-\/](\d{4})$/.exec(date);
      if (matches == null) return false;
      var d = matches[1];
      var m = matches[2] - 1;
      var y = matches[3];
      var composedDate = new Date(y, m, d);
      return composedDate.getDate() == d && composedDate.getMonth() == m && composedDate.getFullYear() == y;
}