docs: function isValidDate(dateString, dateFormat, returnDateFormat) {
      if(moment(dateString, dateFormat).format(dateFormat) !== dateString) {
          return false;
      }
      if(!moment(dateString, dateFormat).isValid()) {
          return false;
      }
      if(returnDateFormat) {
          return moment(dateString, dateFormat).format(returnDateFormat);
      }
      return true;
  }