When you create an appointment that starts on 30 November and ends at 00:00 on 1 December, the appointment time slot is extended to the next day. This happens when it is the end of the previous month and the beginning of the next one. 

Please refer to the attached sample gif file illustrating how to reproduce the problem with the Demo Application. 

Workaround: if the end time is at midnight, reduce the duration with one minute.

 private void radScheduler1_AppointmentAdded(object sender, Telerik.WinControls.UI.AppointmentAddedEventArgs e)
        {
            if (e.Appointment.End.Hour==0 && e.Appointment.End.Minute==0)
            {
                e.Appointment.End = e.Appointment.End.AddMinutes(-1);
            }
        }

To reproduce: use the following code

Sub New()

    InitializeComponent()

    AddHandler Me.RadScheduler1.ActiveViewChanged, AddressOf ActiveViewChanged
    Me.RadScheduler1.ActiveViewType = Telerik.WinControls.UI.SchedulerViewType.Week
End Sub

Private Sub ActiveViewChanged(sender As Object, e As Telerik.WinControls.UI.SchedulerViewChangedEventArgs)
    Dim dayView As SchedulerDayViewBase = TryCast(Me.RadScheduler1.ActiveView, SchedulerDayViewBase)
    Dim dayViewElement As SchedulerDayViewElement = TryCast(Me.RadScheduler1.SchedulerElement.ViewElement, SchedulerDayViewElement)
    If dayViewElement IsNot Nothing Then
        Dim ruler As RulerPrimitive = dayViewElement.DataAreaElement.Ruler
        ruler.StartScale = 6
        ruler.EndScale = 22  
        dayView.WorkTime = New TimeInterval(TimeSpan.FromHours(13), TimeSpan.FromHours(16))
         
    End If
End Sub

When you run the project you will notice that the work time starts from 19:00 to 22:00. When you switch between DayView and WeekView, the ruler is not aligned with the scheduler cells as well. The attached gif file illustrates the incorrect behavior.

Workaround: use the RulerStartScale and RulerEndScale of the SchedulerDayViewBase

 Sub New()

     InitializeComponent()

     AddHandler Me.RadScheduler1.ActiveViewChanged, AddressOf ActiveViewChanged
     Me.RadScheduler1.ActiveViewType = Telerik.WinControls.UI.SchedulerViewType.Week
 End Sub

 Private Sub ActiveViewChanged(sender As Object, e As Telerik.WinControls.UI.SchedulerViewChangedEventArgs)
     Dim dayView As SchedulerDayViewBase = TryCast(Me.RadScheduler1.ActiveView, SchedulerDayViewBase)
     If dayView IsNot Nothing Then
         dayView.RulerStartScale = 6
         dayView.RulerEndScale = 22
         dayView.WorkTime = New TimeInterval(TimeSpan.FromHours(13), TimeSpan.FromHours(16))
     End If
 End Sub

1. Add RadSchedulerNavigator and a RadScheduler. Change the view type to Week View.
2. Associate the RadSchedulerNavigator to RadScheduler. Change the PC's time zone to (UTC-03:00) Brasilia Time zone
3. Change the PC's date to 21 Oct 2016 and run the application.
4. When you change the time zone in RadSchedulerNavigator to (UTC-03:00) Brasilia Time zone, you will notice that the ruler starts from 23.

Workaround: 

public Form1()
{
    InitializeComponent();

    radSchedulerNavigator1.AssociatedScheduler = radScheduler1;

    this.radScheduler1.ActiveViewChanged += radScheduler1_ActiveViewChanged;
    this.radScheduler1.CellElementMouseDown += radScheduler1_CellElementMouseDown; 
    this.radScheduler1.AppointmentEditDialogShowing += radScheduler1_AppointmentEditDialogShowing;
    radScheduler1.ActiveViewType = Telerik.WinControls.UI.SchedulerViewType.Week; 
}

DateTime? date = null;

private void radScheduler1_CellElementMouseDown(object sender, MouseEventArgs e)
{
    SchedulerCellElement cell = this.radScheduler1.ElementTree.GetElementAtPoint(e.Location) as SchedulerCellElement;
    if (cell != null)
    {
        date = cell.Date;
    }
}

CustomEditAppointmentDialog dialog = null;

private void radScheduler1_AppointmentEditDialogShowing(object sender, AppointmentEditDialogShowingEventArgs e)
{
    if (dialog == null)
    {
        dialog = new CustomEditAppointmentDialog();
    }
    e.AppointmentEditDialog = dialog;
    if (date != null && !e.Appointment.Start.Equals(date))
    {
        e.Appointment.Start = (DateTime)date;
    }
    date = null;
}

private void radScheduler1_ActiveViewChanged(object sender, Telerik.WinControls.UI.SchedulerViewChangedEventArgs e)
{
    SchedulerDayView dayView = e.NewView as SchedulerDayView;
    SchedulerWeekView weekView = e.NewView as SchedulerWeekView;
    if (dayView != null || weekView != null)
    {
        RulerPrimitive ruler = (this.radScheduler1.SchedulerElement.ViewElement as SchedulerDayViewElement).DataAreaElement.Ruler;
        ruler.GetType().GetField("defaultOffset", System.Reflection.BindingFlags.Instance | System.Reflection.BindingFlags.NonPublic).SetValue(ruler, 0.0f);
    }
}

public class CustomEditAppointmentDialog : EditAppointmentDialog
{
    protected override void LoadSettingsFromEvent(IEvent sourceEvent)
    {
        base.LoadSettingsFromEvent(sourceEvent);
        this.dateStart.Value = sourceEvent.Start;
        this.timeStart.Value  = sourceEvent.Start;
    }
}

Workaround:

Sub New()

    InitializeComponent()
     
    Me.RadScheduler1.ActiveViewType = UI.SchedulerViewType.Week
    AddHandler Me.RadSchedulerNavigator1.SchedulerNavigatorElement.ShowWeekendCheckBox.ToggleStateChanged, AddressOf ToggleStateChanged
End Sub

Private Sub ToggleStateChanged(sender As Object, args As UI.StateChangedEventArgs) 
    Me.RadScheduler1.SchedulerElement.RefreshViewElement()
End Sub

To reproduce:

public Form1()
{
    InitializeComponent();
    this.radScheduler1.ActiveViewType = SchedulerViewType.Week;
    SchedulerWeekView weekView = this.radScheduler1.GetWeekView();
    weekView.RangeFactor = ScaleRange.QuarterHour;
    
    Appointment appointment = new Appointment(DateTime.Today.AddHours(23).AddMinutes(45), new TimeSpan(0,15,0), "Meeting");
    DailyRecurrenceRule rrule = new DailyRecurrenceRule(appointment.Start, 1, 10); 
    appointment.RecurrenceRule = rrule;
    this.radScheduler1.Appointments.Add(appointment);
}

Workaround: In order to deal with the border case with appointment ending at 00:00h, use a new TimeSpan(0,14,59)

To reproduce:

this.radScheduler1.ActiveViewType = SchedulerViewType.Month;
for (int i = 0; i < 10; i++)
{
    this.radScheduler1.Appointments.Add(new Appointment(DateTime.Now.AddHours(i),TimeSpan.FromMinutes(30),"A"+i));
}
 
Scroll to the bottom and try to select an appointment. You will notice that selection is not possible. The attached gif file illustrates the incorrect behavior. 

Workaround: use the overflow button by setting the SchedulerMonthView.EnableCellOverflowButton property to true:
SchedulerMonthView monthView = this.radScheduler1.GetMonthView();
 monthView.EnableCellOverflowButton = true;

Please refer to the attached screenshot.

Workaround:

public Form1()
{
    InitializeComponent(); 

    this.radScheduler1.ElementProvider = new MyElementProvider(this.radScheduler1);
}

public class MyElementProvider : SchedulerElementProvider
{
    public MyElementProvider(RadScheduler scheduler) : base(scheduler)
    {
    }

    protected override T CreateElement<T>(SchedulerView view, object context)
    {
        if (typeof(T) == typeof(AppointmentElement))
        {
            return new CustomAppointmentElement(this.Scheduler, view, (IEvent)context)as T;
        }

        return base.CreateElement<T>(view, context);
    }
}

public class CustomAppointmentElement : AppointmentElement
{
    protected override Type ThemeEffectiveType     
    { 
        get    
        { 
            return typeof(AppointmentElement);     
        }
    }

    public CustomAppointmentElement(RadScheduler scheduler,
        SchedulerView view, IEvent appointment) : base(scheduler, view, appointment)
    {
    }

    protected override SizeF ArrangeOverride(SizeF finalSize)
    {
        SizeF s = base.ArrangeOverride(finalSize);
        return new SizeF(s.Width - 5,s.Height);
    }
}

To reproduce:

public Form1()
{
    InitializeComponent();
    this.radScheduler1.ActiveViewType = Telerik.WinControls.UI.SchedulerViewType.Month;

    CultureInfo culture = new CultureInfo("en-US");
    culture.DateTimeFormat.FirstDayOfWeek = DayOfWeek.Monday;
    this.radScheduler1.Culture = culture;
   
    Appointment a = new Appointment(new DateTime(2016, 8, 29, 0, 0, 0), new DateTime(2016, 9, 5, 0, 0, 0), "Meeting");

    this.radScheduler1.Appointments.Add(a);

    this.radScheduler1.FocusedDate = new DateTime(2016, 9, 1);

    this.radScheduler1.EnableExactTimeRendering = true;
}

When you run the application starting scrolling with the mouse wheel up/down.

Workaround: do not set the FirstDayOfWeek to Monday.

Note: If you open the context menu over a recurring  appointment and select "Edit Appointment", when the EditAppointmentDialogis shown, the EditRecurrenceDialog is shown as well. But when the EditAppointmentDialog is shown by double clicking, the EditRecurrenceDialog  is not opened at all.

Workaround:
 this.radScheduler1.SchedulerInputBehavior = new CustomBehavior(this.radScheduler1);

public class CustomBehavior : SchedulerInputBehavior
{ 
    public CustomBehavior(RadScheduler scheduler) : base(scheduler)
    {
    }

    public override bool HandleAppointmentElementDoubleClick(object sender, EventArgs args)
    {
        MouseEventArgs mouseArgs = args as MouseEventArgs;
        if (mouseArgs == null || mouseArgs.Button != MouseButtons.Left)
        {
            return false;
        }
        FieldInfo fi = typeof(SchedulerInputBehavior).GetField("beginEditTimer", BindingFlags.NonPublic| BindingFlags.Instance);
        Timer beginEditTimer = fi.GetValue(this) as Timer;
        beginEditTimer.Stop();

        if (!this.Scheduler.ReadOnly && sender is AppointmentElement)
        {
            AppointmentElement app = sender as AppointmentElement; 
            this.Scheduler.ShowAppointmentEditDialog(app.Appointment, app.Appointment.MasterEvent != null);
        }

        return false;
    }
}

To reproduce:

Public Class Form1
    Sub New()
         
        InitializeComponent()

        Me.RadScheduler1.EnableExactTimeRendering = True
        
        Dim dt = DateTime.Now
        Me.RadScheduler1.Appointments.Add(New Appointment(dt.AddMinutes(-10).AddSeconds(1), Now, "A1"))
        Me.RadScheduler1.Appointments.Add(New Appointment(dt.AddMinutes(-15), DateTime.Now.AddMinutes(-10), "A2"))
        Me.RadScheduler1.GetTimelineView().StartDate = DateAdd(DateInterval.Minute, -15, Now)

        Dim customScale As CustomTimescalePerMinute = New CustomTimescalePerMinute()
        Dim timelineView As SchedulerTimelineView = Me.RadScheduler1.GetTimelineView()
        timelineView.SchedulerTimescales.Add(customScale)

        timelineView.ShowTimescale(customScale)
        Dim currentScaling As SchedulerTimescale = timelineView.GetScaling()
        currentScaling.DisplayedCellsCount = 15
    End Sub
End Class

Public Class CustomTimescalePerMinute
Inherits MinutesTimescale
    Public Overrides ReadOnly Property ScalingFactor() As Integer
        Get
            Return 1
        End Get
    End Property
End Class

Note: the attached gif file illustrates the behavior. Initially, the first appointment's end is not rendered in the correct time slot. After scrolling, it is displayed correctly.

Workaround: force scrolling

Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
    Dim t As SchedulerTimelineViewElement = TryCast(Me.RadScheduler1.SchedulerElement.ViewElement, SchedulerTimelineViewElement)
    Dim value = t.NavigationElement.Value
    t.NavigationElement.Value += 1
    Me.RadScheduler1.SchedulerElement.RefreshViewElement()
    t.NavigationElement.Value = value
End Sub

In RadScheduler I have appointment with End set to new DateTime(9999, 12, 22) (or greater). When I switch to Month view the exception is thrown:

The added or subtracted value results in an un-representable DateTime.

Found in version: 2016.2.608.40
It was working in version:  2013.2.724.40

To reproduce:

 public Form1()
 {
     InitializeComponent();

     this.radScheduler1.ActiveViewType = SchedulerViewType.Month;
     this.radScheduler1.Appointments.Add(new Appointment(new DateTime(9999,12,22),TimeSpan.FromMinutes(30),"A1"));
 }
 

To reproduce:
Resource lResource;
var LColors = new Color[5];
SchedulerMultiDayView multyDayView;
DateTime startDate;

int interval;

radScheduler1.Statuses.Add(new AppointmentStatusInfo(5, "New", Color.Green, Color.Green, AppointmentStatusFillType.Solid));
radScheduler1.Statuses.Add(new AppointmentStatusInfo(6, "ACCP", Color.DarkOrange, Color.DarkOrange, AppointmentStatusFillType.Solid));


lResource = new Resource();
lResource.Id = new EventId(1);
lResource.Name = "Bert";
lResource.Color = Color.Red;

radScheduler1.Resources.Add(lResource);

radScheduler1.ActiveView.ShowHeader = true;

this.radScheduler1.ActiveViewType = SchedulerViewType.MultiDay;
multyDayView = this.radScheduler1.GetMultiDayView();

startDate = DateTime.Today;
interval = 30;

radScheduler1.GroupType = GroupType.Resource;
multyDayView.Intervals.Add(startDate, interval);

multyDayView.RulerScaleSize = 4;
radScheduler1.EnableExactTimeRendering = true;

multyDayView.RangeFactor = ScaleRange.Hour;

To reproduce:

RadScheduler radScheduler1 = new RadScheduler();

public Form1()
{
    InitializeComponent();
    this.Controls.Add(this.radScheduler1);
    this.radScheduler1.Dock = DockStyle.Fill;

    Timer timer = new Timer();
    timer.Interval = 1000;
    timer.Tick += timer_Tick;
    this.radScheduler1.ActiveViewType = SchedulerViewType.Timeline;
    SetupView(DateTime.Now.Date);
    timer.Start();
}

private void SetupView(DateTime currentDateTime)
{
    SchedulerTimelineView timelineView = radScheduler1.GetTimelineView();
   
    timelineView.RangeStartDate = currentDateTime;
    timelineView.RangeEndDate = currentDateTime.AddHours(23).AddMinutes(59).AddSeconds(59);
    timelineView.StartDate = currentDateTime;
    radScheduler1.FocusedDate = currentDateTime;
    var scale = Timescales.Hours;
    timelineView.ShowTimescale(scale);
    var currentScaling = timelineView.GetScaling();
    currentScaling.DisplayedCellsCount = 24;

    this.radScheduler1.SchedulerElement.RefreshViewElement();
}

int count = 1;
private void timer_Tick(object sender, EventArgs e)
{
    SetupView(DateTime.Now.AddDays(++count));
}

Workaround: SchedulerTimelineView .ShowNavigationElement = false;

To reproduce:

public RadRibbonForm1() 
{
    InitializeComponent();

    this.radScheduler1.FocusedDate = new DateTime(2016, 1, 1);
    this.radScheduler1.ActiveViewType = Telerik.WinControls.UI.SchedulerViewType.Timeline;
    SchedulerTimelineView timelineView = this.radScheduler1.GetTimelineView();       
    timelineView.RangeStartDate = new DateTime(2016, 1, 1, 00, 00, 00);
    timelineView.RangeEndDate = new DateTime(2016, 12, 31, 23, 59, 59);
    timelineView.StartDate = new DateTime(2016, 1, 1, 00, 00, 00);

    Appointment appointment = new Appointment(new DateTime(2016, 1, 1, 00, 00, 00), new DateTime(2016, 1, 10, 00, 00, 00), "Quarter 1");
    Appointment appointment2 = new Appointment(new DateTime(2016, 2, 1, 00, 00, 00), new DateTime(2016, 2, 10, 00, 00, 00), "Quarter 1");
    Appointment appointment3 = new Appointment(new DateTime(2016, 4, 1, 00, 00, 00), new DateTime(2016, 4, 10, 00, 00, 00), "Quarter 2");
    Appointment appointment4 = new Appointment(new DateTime(2016, 5, 1, 00, 00, 00), new DateTime(2016, 6, 10, 00, 00, 00), "Quarter 2");
    Appointment appointment5 = new Appointment(new DateTime(2016, 7, 1, 00, 00, 00), new DateTime(2016, 7, 10, 00, 00, 00), "Quarter 3");
    Appointment appointment6 = new Appointment(new DateTime(2016, 8, 1, 00, 00, 00), new DateTime(2016, 8, 10, 00, 00, 00), "Quarter 3");
    Appointment appointment7 = new Appointment(new DateTime(2016, 11, 1, 00, 00, 00), new DateTime(2016, 11, 10, 00, 00, 00), "Quarter 4");
    Appointment appointment8 = new Appointment(new DateTime(2016, 12, 1, 00, 00, 00), new DateTime(2016, 12, 10, 00, 00, 00), "Quarter 4");

    this.radScheduler1.Appointments.Add(appointment);
    this.radScheduler1.Appointments.Add(appointment2);
    this.radScheduler1.Appointments.Add(appointment3);
    this.radScheduler1.Appointments.Add(appointment4);
    this.radScheduler1.Appointments.Add(appointment5);
    this.radScheduler1.Appointments.Add(appointment6);
    this.radScheduler1.Appointments.Add(appointment7);
    this.radScheduler1.Appointments.Add(appointment8);

    QuarterTimescale qTimeScale = new QuarterTimescale(); 
    qTimeScale.DisplayedCellsCount = 4;
    timelineView.SchedulerTimescales.Add(qTimeScale);
    this.radScheduler1.GetTimelineView().ShowTimescale(qTimeScale); 
}

class QuarterTimescale : MonthTimescale
{
    public override int ScalingFactor
    {
        get
        {
            return 3;
        }
    }

    public override string Name
    {
        get
        {
            return "Quarter";
        }
    }
}

To reproduce:
DateTime dtStart = DateTime.Today.AddDays(2).AddHours(10); 
DateTime dtEnd = DateTime.Today.AddDays(2).AddHours(12); 
Appointment appointment = new Appointment(dtStart, dtEnd, "TEST", "Description"); 
this.radScheduler1.Appointments.Add(appointment); 

System.Threading.Thread.CurrentThread.CurrentCulture = new System.Globalization.CultureInfo("ar-SA");

Try to open the edit dialog.


Workaround: create a custom dialog that inherits  RadSchedulerDialog and implements IEditAppointmentDialog. Thus, you will be able to handle the whole edit operation.

public class Scheduler : RadScheduler
{
    protected override IEditAppointmentDialog CreateAppointmentEditDialog()
    {
        return new MyDialog();
    }

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

public partial class MyDialog : RadSchedulerDialog, IEditAppointmentDialog
{
    public MyDialog()
    {
        InitializeComponent();
    }

    Appointment appointment;

    protected override void OnLoad(EventArgs e)
    {
        base.OnLoad(e); 

        //an example how specify the start date
        RadDateTimePicker dtStart = this.Controls[0] as RadDateTimePicker;
        dtStart.Value = this.appointment.Start;
    }
   
    public void ShowRecurrenceDialog()
    {
        //ToDo
    }

    public bool EditAppointment(Telerik.WinControls.UI.IEvent appointment, Telerik.WinControls.UI.ISchedulerData schedulerData)
    {
        this.appointment = appointment as Appointment;

        return true;
    }
}

To reproduce: Open Demo application >> Scheduler >> Printing example. Add two appointments one of which is with duration 1 hour, the other one lasts 2 hours. When you click the PrintPreview button, the shorter appointment is missing.

Workaround:
public Form1()
{
    InitializeComponent();

    this.radScheduler1.PrintStyle = new CustomSchedulerDailyPrintStyle();
}

public class CustomSchedulerDailyPrintStyle :SchedulerDailyPrintStyle
{
    protected override void DrawAppointments(DateTime currentDate, IResource resource, Rectangle appArea, Graphics graphics)
    {
        int rowCount = Math.Max(1, (int)Math.Ceiling((TimeEndRange - TimeSpan.FromHours(TimeStartRange.Hours)).TotalHours));
        float rowHeight = (float)appArea.Height / rowCount;

        List<IEvent> appointments = this.GetAppointments(currentDate, false, resource);

        appointments.Sort(CompareAppointments);
        bool setColumn = true;
        Dictionary<IEvent, int> columns = new Dictionary<IEvent, int>();
        Dictionary<IEvent, int> maxColumns = new Dictionary<IEvent, int>();
        int currentColumn = 0;

        while (setColumn)
        {
            setColumn = false;
            DateTime currentTime = DateTime.MinValue;

            foreach (IEvent app in appointments)
            {
                if (!columns.ContainsKey(app) && DateFloor(app.Start) >= currentTime)
                {
                    setColumn = true;
                    columns.Add(app, currentColumn);
                    currentTime = DateCeiling(app.End);
                }
            }

            currentColumn++;
        }

        DateTime maxEndDate = DateTime.MinValue;
        int lastIndex = 0;
        int maxColumn = 0;

        for (int i = 0; i <= appointments.Count; i++)
        {
            if (i == appointments.Count || DateFloor(appointments[i].Start) >= maxEndDate)
            {
                for (int j = lastIndex; j < i; j++)
                {
                    maxColumns.Add(appointments[j], maxColumn);
                }

                maxColumn = 0;
                lastIndex = i;
            }

            if (i == appointments.Count)
            {
                break;
            }

            maxColumn = Math.Max(maxColumn, columns[appointments[i]]);
            if (maxEndDate < DateCeiling(appointments[i].End))
            {
                maxEndDate = DateCeiling(appointments[i].End);
            }
        }

        foreach (IEvent app in appointments)
        {
            AppointmentPrintElement printedAppointment = new AppointmentPrintElement(app, this.Scheduler);
            printedAppointment.ShowHours = false;
            printedAppointment.DrawBorder = printedAppointment.DrawFill = true;

            float appY = appArea.Y + Math.Max(0, (float)(((DateFloor(printedAppointment.Start) - currentDate.Add(this.TimeStartRange)).TotalHours) * rowHeight));
            float appBottom = appArea.Y + Math.Min(appArea.Height, (float)(((DateCeiling(printedAppointment.End) - currentDate.Add(this.TimeStartRange)).TotalHours) * rowHeight));
            float appHeight = appBottom - appY - app.End.Minute;
            float appWidth = (appArea.Width - HoursColumnWidth) / (maxColumns[app] + 1);
            float appX = appArea.X + HoursColumnWidth + columns[app] * appWidth;
            
            RectangleF appRect = new RectangleF(appX, appY, appWidth, appHeight);
            appRect.Inflate(-2f, -2f);
            this.DrawAppointment(printedAppointment, graphics, appRect);
        }
    }
}

To reproduce: follow the steps from the attached gif file.

Workaround:

public Form1()
{
    InitializeComponent();
    this.radScheduler1.RecurrenceEditDialogShowing += radScheduler1_RecurrenceEditDialogShowing;
}

CustomEditRecurrenceDialog dialog = null;

private void radScheduler1_RecurrenceEditDialogShowing(object sender, Telerik.WinControls.UI.RecurrenceEditDialogShowingEventArgs e)
{
    if (dialog == null)
    {
        dialog = new CustomEditRecurrenceDialog(e.Appointment);
    }
    e.RecurrenceEditDialog = dialog;
}

public class CustomEditRecurrenceDialog : EditRecurrenceDialog
{
    public CustomEditRecurrenceDialog(IEvent appointment) : base(appointment)
    {
    }

    protected override void ApplyAppointmentDates()
    {
        DateTime end = this.appointment.End;
        base.ApplyAppointmentDates();
        this.appointment.End = new DateTime(end.Year, end.Month, end.Day,
            this.timeEnd.Value.Hour, this.timeEnd.Value.Minute, this.timeEnd.Value.Second);
    }
}

Please refer to the attached gif file illustrating how to reproduce the problem with the Demo application. When you define a new appointment with 24 months interval, it is expected to have this event every 2 years, not each year.

To reproduce: you can use the following code snippet as well:

MonthlyRecurrenceRule monthlyRecurrenceRule = new MonthlyRecurrenceRule(DateTime.Now, WeekDays.Monday, 2, 24);
Appointment a = new Appointment(DateTime.Now, TimeSpan.FromHours(3), "Test");
a.RecurrenceRule = monthlyRecurrenceRule;
this.radScheduler1.Appointments.Add(a);


Workaround:

 public Form1()
 {
     InitializeComponent();
     
     this.radScheduler1.AppointmentAdded += radScheduler1_AppointmentAdded;
 }

 private void radScheduler1_AppointmentAdded(object sender, AppointmentAddedEventArgs e)
 {
     MonthlyRecurrenceRule montlyRule = e.Appointment.RecurrenceRule as MonthlyRecurrenceRule;
     if (montlyRule != null)
     {
         CustomMonthlyRecurrenceRule rrule = new CustomMonthlyRecurrenceRule();
         rrule.Start = montlyRule.Start;
         rrule.End = montlyRule.End;
         rrule.Interval = montlyRule.Interval;
         rrule.Offset = montlyRule.Offset;
         rrule.WeekDays = montlyRule.WeekDays;
         rrule.WeekNumber = montlyRule.WeekNumber;
         rrule.FirstDayOfWeek = montlyRule.FirstDayOfWeek;
         rrule.Count = montlyRule.Count; 

         e.Appointment.RecurrenceRule = rrule;
     }
 }

 public class CustomMonthlyRecurrenceRule : MonthlyRecurrenceRule
 {
     public override bool MatchAdvancedPattern(DateTime date, DateTimeFormatInfo dateTimeFormat)
     {
         int monthIndex = this.Start.Value.Month - date.Month;
         DateTime calculatedNextDate = this.Start.Value.AddMonths(this.Interval);
         monthIndex = calculatedNextDate.Month - date.Month;
         if (calculatedNextDate.Year > date.Year)
         {
             return false;
         }
         if ((monthIndex % this.Interval) != 0)
         {
             return false;
         }

         if (0 != this.WeekNumber && !this.MatchWeekOfMonth(date, dateTimeFormat))
         {
             return false;
         }

         if (0 != this.DayNumber && !this.MatchDayOfMonth(date, dateTimeFormat))
         {
             return false;
         }

         if (this.WeekDays != WeekDays.None && !this.MatchDayOfWeekMask(date, dateTimeFormat.Calendar))
         {
             return false;
         }

         if (this.Offset != 0 && !this.MatchOffset(date, dateTimeFormat))
         {
             return false;
         }

         return true;
     }
 }