code: @Override
      public long toEpochDay() {
          long epochDay =
                  (long) (this.prolepticYear - 1) * DAYS_IN_YEAR +
                  Symmetry454Chronology.getLeapYearsBefore(this.prolepticYear) * DAYS_IN_WEEK +
                  this.dayOfYear -
                  DAYS_0001_TO_1970 - 1;
  
          return epochDay;
      }
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