docs: public Date getExpiry() {
          String dateTime = getFieldValue(SubscribeOptionFields.expire);
          try {
              return XmppDateTime.parseDate(dateTime);
          }
          catch (ParseException e) {
              UnknownFormatConversionException exc = new UnknownFormatConversionException(dateTime);
              exc.initCause(e);
              throw exc;
          }
      }