code: static BritishCutoverDate ofYearDay(int prolepticYear, int dayOfYear) {
          if (prolepticYear < CUTOVER_YEAR || (prolepticYear == CUTOVER_YEAR && dayOfYear <= 246)) {
              JulianDate julian = JulianDate.ofYearDay(prolepticYear, dayOfYear);
              return new BritishCutoverDate(julian);
          } else if (prolepticYear == CUTOVER_YEAR) {
              LocalDate iso = LocalDate.ofYearDay(prolepticYear, dayOfYear + CUTOVER_DAYS);
              return new BritishCutoverDate(iso);
          } else {
              LocalDate iso = LocalDate.ofYearDay(prolepticYear, dayOfYear);
              return new BritishCutoverDate(iso);
          }
      }
docs: Obtains a {@code BritishCutoverDate} representing a date in the British Cutover calendar
  system from the proleptic-year and day-of-year fields.
  <p>
  This returns a {@code BritishCutoverDate} with the specified fields.
  The day must be valid for the year, otherwise an exception will be thrown.
  
  @param prolepticYear  the British Cutover proleptic-year
  @param dayOfYear  the British Cutover day-of-year, from 1 to 366
  @return the date in British Cutover 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