NETWORKDAYS Function
From Planfix
The NETWORKDAYS function returns the number of workdays between "start_date" and "end_date," inclusive. Holidays and days off are not included. The account's default work calendar is used when calculating (first in the list of the account's work hours)
Format:
NETWORKDAYS(start_date;end_date)
where start_date and end_date are column or row names
Example
Getting the number of work days in the current month:
NETWORKDAYS(DATE(YEAR(D); MONTH(D); 1); EOMONTH(D; 0))
Important:
The function currently doesn't work for formulas calculated only for totals lines or the first groupings in reports.