* @return a CopticDate object, never null
* @throws IllegalCalendarFieldValueException if the year range is exceeded
*/
private static CopticDate copticDateFromEopchDays(int epochDays) {
if (epochDays < MIN_EPOCH_DAY || epochDays > MAX_EPOCH_DAY) {
throw new IllegalCalendarFieldValueException(
"Date exceeds supported range for CopticDate", CopticChronology.yearRule());
}
int year = ((epochDays * 4) + 1463) / 1461;
int startYearEpochDays = (year - 1) * 365 + (year / 4);
int doy0 = epochDays - startYearEpochDays;