This returns the actual number of work hours between two given Date and Times (both inclusive), according to the calendar defined for the system.
calworkhours( start datetime, end datetime, [calendar name] )
start_datetime: (Date and Time) The starting Date and Time.
end_datetime: (Date and Time) The ending Date and Time.
calendar_name: (Text) This optional parameter accepts the name of a system calendar; otherwise, the default calendar is used.
Integer
Passing a calendar name allows you to calculate working hours using an alternate system calendar, if you have multiple calendars configured.
See also: Process Calendar Settings
calworkhours(datetime(2011,12,20,12,0,0),datetime(2011,12,21,12,0,0))
returns 8