[itfs]

select count(RecId)
        from _WorkCalendarDate
        group by TransDate
         where _WorkCalendarDate.WorkTimeControl == WorkTimeControl::Open
            && _WorkCalendarDate.CalendarId == _WorkCalendarId
            && _WorkCalendarDate.TransDate >= _dtFrom
            && _WorkCalendarDate.TransDate <= _dtTo;

C уважением, itfs.