final ZonedDateTime payDate = ScheduleCalculator.getAdjustedDate(REFERENCE_DATE, Period.ofMonths(9), BUSINESS_DAY, CALENDAR);
final ZonedDateTime expDate = ScheduleCalculator.getAdjustedDate(payDate, -SETTLEMENT_DAYS, CALENDAR);
final double timeToExpiry = TimeCalculator.getTimeBetween(REFERENCE_DATE, expDate);
final ForexDefinition forexUnderlyingDefinition = new ForexDefinition(EUR, USD, payDate, notional, strike);
final ForexOptionDigitalDefinition forexOptionDefinition = new ForexOptionDigitalDefinition(forexUnderlyingDefinition, expDate, isCall, isLong, payDomestic);
final ForexOptionDigital forexOption = forexOptionDefinition.toDerivative(REFERENCE_DATE, CURVES_NAME);
final double dfDomestic = CURVES.getCurve(CURVES_NAME[0]).getDiscountFactor(forexOption.getUnderlyingForex().getPaymentTime());
final double dfForeign = CURVES.getCurve(CURVES_NAME[1]).getDiscountFactor(forexOption.getUnderlyingForex().getPaymentTime());
final double forward = 1 / SPOT * dfForeign / dfDomestic;
final double volatility = SMILE_TERM.getVolatility(new Triple<>(timeToExpiry, 1.0 / forward, 1.0 / forward));
final double sigmaRootT = volatility * Math.sqrt(forexOption.getExpirationTime());