BloombergLP::bdlt::CalendarUtil::subtractBusinessDaysIfValid

Load, into the specified result, the date that is the specified numBusinessDays chronologically before the specified original date according to the specified calendar. The resulting date is chronologically before the original date for positive values of numBusinessDays, the chronologically latest business day that is on or before the original date for 0 == numBusinessDays, and chronologically after the original date for negative values of numBusinessDays. Return 0 on success, and a non‐zero value, without modifying *result, if either the original date or the resulting date is not within the valid range of calendar. Note that if 0 != numBusinessDays, then the result of subtractBusinessDaysIfValid(res, orig, cal, numBusinessDays) is identical to the result of addBusinessDaysIfValid(res, orig, cal, ‐numBusinessDays).