How it is worked out
working days = calendar days − weekends − holidays listed
Why it is done this way
A working day is any day that is not a Saturday, a Sunday or a public holiday. The count matters because almost every deadline that involves an organisation is expressed in working days, and a month of calendar days is only about twenty-two of them.
Step by step
- Count the calendar days between the two dates
- Take out every Saturday and Sunday in the range
- Take out any public holidays that fall on a weekday
- What remains is the working days
What is worth knowing
Holidays have to be entered by hand for a good reason: they differ by country, by region and by year, and a calculator that guessed would be confidently wrong. Note that a holiday falling on a weekend is already excluded, so listing it changes nothing. The rough conversion worth remembering is that calendar days are about 1.4 times working days over any period longer than a couple of weeks — thirty calendar days is roughly twenty-two working ones.