With this function, weekend days (Saturday and Sunday) are automatically removed from the total.
Specific days, such as statutory holidays, can be omitted, too.
The syntax for the NETWORKDAYS function is NETWORKDAYS(start_date, end_date,[holidays]).

Ted French/Lifewire
pick the cell where you’d like the result to be displayed.
Enter the formula and appropriate parameters.
This tells Sheets to calculate the workdays between 7/11/2016 and 11/4/2016.
error value is returned if any argument contains an invalid date.
The Math Behind the Function
Google Sheets processes its calculation in two steps.
First, it assesses the straightforward count of working days between the two stipulated dates.
After that, it removes every date specified in theholidaysargument, if the date occurred on a weekday.