Map<String, List<Attendance>> associatedAttendances = collectAttendancesByUsers(attendances);
        List<Date> nonWorkingDays = nonWorkingDayDao.findAll(startDate, endDate);

        Map<Employee, List<Date>> gaps = new TreeMap<>(new EmployeeComparator());
        for (Employee emp : employees) {
            List<Attendance> employeeAttendances = associatedAttendances.get(emp.getLogin());
            boolean employeePresents = true;
            if (employeeAttendances == null) {
                employeePresents = false;
            }
            List<Date> employeeMissingDays = new ArrayList<>();

            Calendar control = getCalendarInstance(startDate);
            control.setTime(startDate);
            while (control.getTime().before(endDate)) {
                if (!employeePresents) {
                    employeeMissingDays.add(control.getTime());
                    control.add(Calendar.DAY_OF_YEAR, 1);
                    continue;
                }
                if (!isCalendarDatePresentData(control, employeeAttendances, nonWorkingDays)) {
                    employeeMissingDays.add(control.getTime());
                }
                control.add(Calendar.DAY_OF_YEAR, 1);
            }
            if (!employeeMissingDays.isEmpty()) {
                gaps.put(emp, employeeMissingDays);
            }
        }
        generateReport(groupData(gaps));