The method to refering to is an event handler and not a best choice for direct calling. What I would do in this case, is :
//A PROPERTY THAT SAVES SELECTED DATE VALUE
public DateTime SelectedDate {get;set;}
//A METHOD THAT SHOWS ACTIVITY
public void ShowActivity(DateTime date) {
DayView Activity = new DayView(date);
Activity.Show();
this.Hide();
}
public void calItemSelectedDate(object sender, SelectionChangedEventArgs e)
{
DateTime d;
if (sender is DateTime)
{
d = (DateTime)sender;
}
else
{
DateTime.TryParse(sender.ToString(), out d);
}
SelectedDate = d;
ShowActivity(d);
}
and from your class where you want to call it:
DateTime p = Globals._globalController.getMonthViewWindow.SelectedDate;
DayView d = new DayView(p);