How it's calculated
result date = start date ± N days
start date = chosen date, N = number of days, direction adds (from) or subtracts (before). Business-day mode counts N days while skipping Saturdays and Sundays.
Common questions
How long is 120 days?
It is about four months, or roughly 17 weeks, depending on which months it spans.
Why use business days for 120 days?
Some deadlines like probation periods or filing windows count only working days, so the business-day mode skips weekends.