function convertDate(rawDate) {
  if (rawDate.length == 0) {
    return null;
  }
  var date = parseInt(rawDate, 10);
  var year = Math.round(date / 10000);
  var month = Math.round((date / 100) % 100 - 1);
  var day = Math.round(date % 100);
  return new Date(year, month, day);
}
@param {string} rawDate Date in YYYYMMDD number format.
@return {?Date}