code: private static BigDecimal calculateProrationBetweenDates(final LocalDate startDate, final LocalDate endDate, final LocalDate previousBillingCycleDate, final LocalDate nextBillingCycleDate) {
          final int daysBetween = Days.daysBetween(previousBillingCycleDate, nextBillingCycleDate).getDays();
          return calculateProrationBetweenDates(startDate, endDate, daysBetween);
      }
docs: Called internally to calculate proration or when we recalculate approximate repair amount
  
  @param startDate                start date of the prorated interval
  @param endDate                  end date of the prorated interval
  @param previousBillingCycleDate start date of the period
  @param nextBillingCycleDate     end date of the period