public void Previous(object obj)
 {
     Settings.Default.CurrentWeek--;
     _currentWeeks.Clear();
     SingleWeek.Add(new WeekViewModel(_semesters, true));
     SingleWeek.Add(new WeekViewModel(_semesters, false));
 }
        public void Update(object obj)
        {
            _currentWeeks.Clear();
            int i = 0;

            if (_breaksChecked)
            {
                i++;
            }

            if ((OldDate != null) && (NewDate != null))
            {
                _semesters.NewSemesters(_oldStart, _newStart, _numberOfWeeks + i, _breaksChecked);
                Settings.Default.CurrentWeek = 0;
                SingleWeek.Add(new WeekViewModel(_semesters, true));
                SingleWeek.Add(new WeekViewModel(_semesters, false));
            }
        }