RangeMinDate and RangeMaxDate properties of RadCalendar are not taken under consideration when a date is being selected.

Although RadCalendarDay has a Tooltip property, it does not show any tooltips.

Fast navigation element displays duplicated items

Setting SelectedDate via code in RadCalendar does not work when AllowMultipleSelect is false.

The month selector of RadCalendar should fire Calendar.Navigating and Calendar.Navigated events.

To reproduce: select 01/01/0001 and click the previous button

The event should fire so one can customize the appearance on loading.

To reproduce: use the following code snippet:

public Form1()
{
    InitializeComponent();
    this.radCalendar1.AllowMultipleView = true;
    this.radCalendar1.MultiViewRows = 3;
    this.radCalendar1.HeaderNavigationMode = Telerik.WinControls.UI.HeaderNavigationMode.Zoom;
}

To reproduce: use the following code snippet:

public Form1()
{
    InitializeComponent();

    this.radCalendar1.AllowMultipleView = true;
    this.radCalendar1.MultiViewRows = 3;
    this.radCalendar1.MultiViewColumns = 4;
    this.radCalendar1.AllowMultipleSelect = true;
    this.radCalendar1.ShowRowHeaders = true;
    this.radCalendar1.ShowColumnHeaders = true;
    this.radCalendar1.AllowColumnHeaderSelectors = true;
    this.radCalendar1.AllowRowHeaderSelectors = true;
    this.radCalendar1.ShowViewSelector = true;
    this.radCalendar1.AllowViewSelector = true;

  
    this.radCalendar1.RangeMinDate = new DateTime(2014, 3, 3);
    this.radCalendar1.RangeMaxDate = new DateTime(2014, 7, 27);
    this.radCalendar1.FocusedDate = new DateTime(2014, 5, 5);
}

Please refer to the attached gif file.

Workaround: 
private void Calendar_MouseDown(object sender, MouseEventArgs e)
{
    CalendarCellElement cell = this.radCalendar1.CalendarElement.ElementTree.GetElementAtPoint(e.Location) as CalendarCellElement;
    if (cell != null && cell.Date < this.radCalendar1.RangeMinDate && (bool)cell.GetValue(CalendarCellElement.IsHeaderCellProperty) == true)
    {
        foreach (MonthViewElement monthView in this.radCalendar1.CalendarElement.CalendarVisualElement.Children[0].Children.Last().Children)
        {
            {
                foreach (CalendarCellElement monthCell in monthView.TableElement.Children)
                {
                    if (monthCell.Date.Month == cell.Date.Month && monthCell.Date.Year == cell.Date.Year &&
                        this.radCalendar1.RangeMinDate <= monthCell.Date)// &&
                       // (bool)cell.GetValue(CalendarCellElement.IsHeaderCellProperty) == false)
                    {
                        if (char.IsLetter(cell.Text[0]))
                        {
                            //perform column selection
                            if (monthCell.ControlBoundingRectangle.X == cell.ControlBoundingRectangle.X)
                            {
                                this.radCalendar1.SelectedDates.Add(monthCell.Date);
                            }
                        }
                        else
                        {
                            //perform row selection
                            if (monthCell.ControlBoundingRectangle.Y == cell.ControlBoundingRectangle.Y)
                            {
                                this.radCalendar1.SelectedDates.Add(monthCell.Date);
                            }
                        }
                    }
                }
            }
        }
    }
}

To reproduce: use the following code snippet:

            radCalendar1.AllowMultipleSelect = true;
            radCalendar1.ShowRowHeaders = true;
            radCalendar1.AllowRowHeaderSelectors = true;
 If you select several cells, they all are selected. Then, click the header row cell. You will notice that the cells from this row are selected but all previously selected cells are cleared. The attached gif file illustrates the behavior. 

Workaround: use the MouseDown event to store the currently selected cells and then on MouseUp restore the missing selection:

public class MyCalendar : RadCalendar
{
    List<DateTime> selectedDays = new List<DateTime>();

    protected override void OnMouseDown(MouseEventArgs e)
    {
        CalendarCellElement cell = this.ElementTree.GetElementAtPoint(e.Location) as CalendarCellElement;
        if (cell != null)
        {
            bool isHeader = (bool)cell.GetValue(CalendarCellElement.IsHeaderCellProperty);
            if (isHeader)
            {
                selectedDays.Clear();
                foreach (DateTime date in this.SelectedDates)
                {
                    selectedDays.Add(date);
                }
            }
        }
        base.OnMouseDown(e);
    }

    protected override void OnMouseUp(MouseEventArgs e)
    {
        base.OnMouseUp(e);
        foreach (DateTime date in selectedDays)
        {
            if (!this.SelectedDates.Contains(date))
            {
                this.SelectedDates.Add(date);
            }
        }
    }

    public override string ThemeClassName  
    { 
        get 
        { 
            return typeof(RadCalendar).FullName;  
        }
    }
}

By default, if you need to format the cells in RadCalendar, the ElementRender event is an appropriate solution. However, it doesn't process the row/column header cell elements illustrated in the attached screenshot.

Workaround:

Run the attached sample project and try entering "1400/12/30".

            CultureInfo info = new CultureInfo("fa-Ir");

            this.radDateTimePicker1.Format = DateTimePickerFormat.Custom;
            this.radDateTimePicker1.CustomFormat = "yyyy/MM/dd";
            this.radDateTimePicker1.Culture = info;

The following exception occurs: 

   at System.Globalization.PersianCalendar.ToDateTime(Int32 year, Int32 month, Int32 day, Int32 hour, Int32 minute, Int32 second, Int32 millisecond, Int32 era)
   at System.Globalization.Calendar.ToDateTime(Int32 year, Int32 month, Int32 day, Int32 hour, Int32 minute, Int32 second, Int32 millisecond)
   at Telerik.WinControls.UI.ArabicMaskDateTimeProvider.KeyPress(Object sender, KeyPressEventArgs e)
   at Telerik.WinControls.UI.RadMaskedEditBoxElement.TextBoxItem_KeyPress(Object sender, KeyPressEventArgs e)
   at System.Windows.Forms.KeyPressEventHandler.Invoke(Object sender, KeyPressEventArgs e)
   at Telerik.WinControls.RadItem.OnKeyPress(KeyPressEventArgs e)
   at Telerik.WinControls.UI.RadTextBoxItem.TextBoxControl_KeyPress(Object sender, KeyPressEventArgs e)
   at System.Windows.Forms.Control.OnKeyPress(KeyPressEventArgs e)
   at System.Windows.Forms.Control.ProcessKeyEventArgs(Message& m)
   at System.Windows.Forms.Control.ProcessKeyMessage(Message& m)
   at System.Windows.Forms.Control.WmKeyChar(Message& m)
   at System.Windows.Forms.Control.WndProc(Message& m)
   at System.Windows.Forms.TextBoxBase.WndProc(Message& m)
   at System.Windows.Forms.TextBox.WndProc(Message& m)
   at Telerik.WinControls.UI.HostedTextBoxBase.WndProc(Message& message)
   at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)
   at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)
   at System.Windows.Forms.NativeWindow.DebuggableCallback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)
   at System.Windows.Forms.UnsafeNativeMethods.DispatchMessageW(MSG& msg)
   at System.Windows.Forms.Application.ComponentManager.System.Windows.Forms.UnsafeNativeMethods.IMsoComponentManager.FPushMessageLoop(IntPtr dwComponentID, Int32 reason, Int32 pvLoopData)
   at System.Windows.Forms.Application.ThreadContext.RunMessageLoopInner(Int32 reason, ApplicationContext context)
   at System.Windows.Forms.Application.ThreadContext.RunMessageLoop(Int32 reason, ApplicationContext context)
   at System.Windows.Forms.Application.Run(Form mainForm)
   at DateTimePickerPersianCalendar.Program.Main() in c:\Projects\DateTimePickerPersianCalendar\DateTimePickerPersianCalendar\Program.cs:line 17
   at System.AppDomain._nExecuteAssembly(RuntimeAssembly assembly, String[] args)
   at System.AppDomain.ExecuteAssembly(String assemblyFile, Evidence assemblySecurity, String[] args)
   at Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly()
   at System.Threading.ThreadHelper.ThreadStart_Context(Object state)
   at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
   at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
   at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
   at System.Threading.ThreadHelper.ThreadStart()

RadCalendar crashes when the focused date is set to a value out of the current view and adding rows/columns is performed.

Set the RadCalendar's NavigationNextImage and NavigationPrevImage properties in design time through property grid. The assigned images is shown in the designer. When run the application the images do not be shown.

radCalendar €“ set AllowMultipleView to be true. Set MultiViewColumn and MultiViewRow to be 2. Try to change the Culture and you will see error:
Object reference not set to an instance of an object.

When changing CurrentViewRow or CurrentViewColumn of RadCalendar, the header is shown even when the ShowHeader is set to false.

The border of the special days in RadCalendar does not change on mouse leave.

When RadCalendar is docked inside a panel which is docked in a form and the calendar is in MultiMonth view, the month headers are not displayed properly.

RadCalendar throws an exception when you change the culture to ar-SA.

Use the following code snippet:

private void radCalendar1_ViewChanged(object sender, EventArgs e)
{
    this.radCalendar1.SpecialDays.Clear();

    RadCalendarDay day = new RadCalendarDay(new DateTime(2014,04,15));
    radCalendar1.SpecialDays.Add(day);
    PictureBox pictureBox = new PictureBox();
    pictureBox.SizeMode = PictureBoxSizeMode.StretchImage;
    pictureBox.Image = Properties.Resources.home;
    RadHostItem hostItem = new RadHostItem(pictureBox);
    day.TemplateItem = hostItem;
}

Clicking the navigation buttons does not navigate you to the respective month.

Workaround: assign the RadCalendarDay.TemplateItem before adding the day in the SpecialDays collection:
private void radCalendar1_ViewChanged(object sender, EventArgs e)
{
    this.radCalendar1.SpecialDays.Clear();

    RadCalendarDay day = new RadCalendarDay(new DateTime(2014,04,15));
    PictureBox pictureBox = new PictureBox();
    pictureBox.SizeMode = PictureBoxSizeMode.StretchImage;
    pictureBox.Image = Properties.Resources.home;
    RadHostItem hostItem = new RadHostItem(pictureBox);
    day.TemplateItem = hostItem; 
    radCalendar1.SpecialDays.Add(day);
}

Note: if the initial code is used in the ViewChanging event, clicking the navigation buttons leads to freezing the application.