docs: public Days toStandardDays() {
          checkYearsAndMonths("Days");
          long millis = getMillis();  // assign to a long
          millis += ((long) getSeconds()) * DateTimeConstants.MILLIS_PER_SECOND;
          millis += ((long) getMinutes()) * DateTimeConstants.MILLIS_PER_MINUTE;
          millis += ((long) getHours()) * DateTimeConstants.MILLIS_PER_HOUR;
          long days = millis / DateTimeConstants.MILLIS_PER_DAY;
          days = FieldUtils.safeAdd(days, getDays());
          days = FieldUtils.safeAdd(days, ((long) getWeeks()) * ((long) DateTimeConstants.DAYS_PER_WEEK));
          return Days.days(FieldUtils.safeToInt(days));
      }