code: static EthiopicDate ofYearDay(int prolepticYear, int dayOfYear) {
          EthiopicChronology.YEAR_RANGE.checkValidValue(prolepticYear, YEAR);
          DAY_OF_YEAR.range().checkValidValue(dayOfYear, DAY_OF_YEAR);
          if (dayOfYear == 366 && EthiopicChronology.INSTANCE.isLeapYear(prolepticYear) == false) {
              throw new DateTimeException("Invalid date 'Pagumen 6' as '" + prolepticYear + "' is not a leap year");
          }
          return new EthiopicDate(prolepticYear, (dayOfYear - 1) / 30 + 1, (dayOfYear - 1) % 30 + 1);
      }
docs: Obtains a {@code EthiopicDate} representing a date in the Ethiopic calendar
  system from the proleptic-year and day-of-year fields.
  <p>
  This returns a {@code EthiopicDate} with the specified fields.
  The day must be valid for the year, otherwise an exception will be thrown.
  
  @param prolepticYear  the Ethiopic proleptic-year
  @param dayOfYear  the Ethiopic day-of-year, from 1 to 366
  @return the date in Ethiopic calendar system, not null
  @throws DateTimeException if the value of any field is out of range,
  or if the day-of-year is invalid for the year