the calendar used for reference and/or option date calculation
date-range check
time-range check
the day counter used for date/time conversion
the latest date for which the curve can return values
the latest time for which the curve can return values
the date at which discount = 1.0 and/or variance = 0.0
the settlementDays used for reference date calculation
date/time conversion
Calculations
These methods must be implemented in derived classes to perform the actual volatility calculations. When they are called, range check has already been performed; therefore, they must assume that extrapolation is required.