Hello,

You can handle the SelectedDatesChanged event, which is fired when you click on a day or you can use PreviewMouseLeftButtonDown event :

void xamMonthCalendar1_PreviewMouseLeftButtonDown(object sender, MouseButtonEventArgs e)

        {

            CalendarDay day = Infragistics.Windows.Utilities.GetAncestorFromType(e.OriginalSource as DependencyObject, typeof(CalendarDay), true) as CalendarDay;

            if (day != null)

            {

                Debug.WriteLine("Selected Date in preview button down");

            }

        }