Calculating Network Hours / Working Hours

Anonymous -

Here's the date table that is referenced in the Calculated Column. Notice, it has a Weekend attribute to indicate whether it's a weekend. You could add OffDay, which considers both weekends and holidays.

Date = ADDCOLUMNS(CALENDAR(DATE(2018,1,1),DATE(2020,12,31)),"Weekend",IF(WEEKDAY([Date]) IN {1,7}, TRUE(),FALSE()))

Here's a Calculated Column. It works with weekends. The same logic could be used with Is OffDay instead of Weekend. You'd replace the following bits: 

var start_date_is_weekend = LOOKUPVALUE('Date'[Weekend],'Date'[Date],INT([Date/Time Opened]))

var end_date_is_weekend = LOOKUPVALUE('Date'[Weekend],'Date'[Date],INT([Date/Time Closed]))

'Date'[Weekend] = FALSE()

Hours Difference = 
//Define hours of workday, in seconds
var work_day_begins = 3600 * 9 //9AM
var work_day_ends = 3600 * 17  //5PM
var seconds_in_workday = work_day_ends - work_day_begins

//Check whether start/end dates occurred on a weekend.
var start_date_is_weekend = LOOKUPVALUE('Date'[Weekend],'Date'[Date],INT([Date/Time Opened]))
var end_date_is_weekend = LOOKUPVALUE('Date'[Weekend],'Date'[Date],INT([Date/Time Closed]))

//Get the seconds from midnight. 
//If it's a weekend, always use the end of the workday value.
//If outside working hours, snap to the start or end of day.
var start_time = TIMEVALUE(FORMAT([Date/Time Opened],"HH:mm:ss"))*86400
var end_time = TIMEVALUE(FORMAT([Date/Time Closed],"HH:mm:ss"))*86400
var start_time_adj = IF(start_date_is_weekend,work_day_ends,MIN(MAX(start_time,work_day_begins),work_day_ends))
var end_time_adj = SWITCH(
    TRUE(),
    ISBLANK(end_date_is_weekend),BLANK(),
    end_date_is_weekend,work_day_ends,
    MIN(MAX(end_time,work_day_begins),work_day_ends)
)

//Find the number of workdays
var day_diff = COUNTROWS(
    FILTER(
        'Date',
        [Date] > INT([Date/Time Opened]) 
        && [Date] <= INT([Date/Time Closed]) 
        && 'Date'[Weekend] = FALSE()
    )
)

//Final calculation:
var time_diff = end_time_adj - start_time_adj
var working_seconds = (day_diff * seconds_in_workday) + time_diff
var working_hours = working_seconds / 3600.00
return IF(ISBLANK([Date/Time Closed]),BLANK(),working_hours)