code: public static EthiopianCalendar of(
          EthiopianEra era,
          int yearOfEra,
          int month,
          int dayOfMonth
      ) {
  
          if (!CALSYS.isValid(era, yearOfEra, month, dayOfMonth)) {
              throw new IllegalArgumentException(
                  "Invalid Ethiopian date: era="
                      + era + ", year=" + yearOfEra + ", month=" + month + ", day=" + dayOfMonth);
          }
  
          return new EthiopianCalendar(mihret(era, yearOfEra), month, dayOfMonth);
  
      }
docs: /*[deutsch]
  <p>Erzeugt ein neues &auml;thiopisches Kalenderdatum. </p>
  
  @param   era         Ethiopian era
  @param   yearOfEra   Ethiopian year of era in the range 1-9999 (1-15499 if amete alem)
  @param   month       Ethiopian month in the range 1-13
  @param   dayOfMonth  Ethiopian day of month in the range 1-30
  @return  new instance of {@code EthiopianCalendar}
  @throws  IllegalArgumentException in case of any inconsistencies
  @since   3.11/4.8