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

Currently, the control lacks such support and when this culture is used an exception is thrown. To reproduce use the sample project and press the navigator's Next button several times.

StackTrace:

System.ArgumentOutOfRangeException occurred

  HResult=-2146233086
  Message=Year, Month, and Day parameters describe an un-representable DateTime.
  Source=mscorlib
  StackTrace:
       at System.DateTime.DateToTicks(Int32 year, Int32 month, Int32 day)
       at Telerik.WinControls.UI.DateHelper.GetEndOfMonth(DateTime date, DateTimeFormatInfo dateTimeFormat)
       at Telerik.WinControls.UI.DateHelper.GetMonthDisplayWeeks(DateTime date, DateTimeFormatInfo dateTimeFormat)
       at Telerik.WinControls.UI.SchedulerNavigatorElement.NavigateBackwards()
       at Telerik.WinControls.UI.SchedulerNavigatorElement.OnNavigateBackwards(Object sender, EventArgs e)
       at Telerik.WinControls.UI.SchedulerNavigatorElement.NavigateButton_Click(Object sender, EventArgs e)
       at System.EventHandler.Invoke(Object sender, EventArgs e)
       at Telerik.WinControls.RadElement.OnClick(EventArgs e)
       at Telerik.WinControls.UI.RadButtonItem.OnClick(EventArgs e)
       at Telerik.WinControls.UI.RadButtonElement.OnClick(EventArgs e)
       at Telerik.WinControls.RadElement.DoClick(EventArgs e)
       at Telerik.WinControls.RadElement.RaiseBubbleEvent(RadElement sender, RoutedEventArgs args)
       at Telerik.WinControls.RadItem.RaiseBubbleEvent(RadElement sender, RoutedEventArgs args)
       at Telerik.WinControls.RadElement.RaiseRoutedEvent(RadElement sender, RoutedEventArgs args)
       at Telerik.WinControls.RadElement.RaiseBubbleEvent(RadElement sender, RoutedEventArgs args)
       at Telerik.WinControls.RadItem.RaiseBubbleEvent(RadElement sender, RoutedEventArgs args)
       at Telerik.WinControls.RadElement.RaiseRoutedEvent(RadElement sender, RoutedEventArgs args)
       at Telerik.WinControls.RadElement.DoMouseUp(MouseEventArgs e)
       at Telerik.WinControls.ComponentInputBehavior.OnMouseUp(MouseEventArgs e)
       at Telerik.WinControls.RadControl.OnMouseUp(MouseEventArgs e)
       at System.Windows.Forms.Control.WmMouseUp(Message& m, MouseButtons button, Int32 clicks)
       at System.Windows.Forms.Control.WndProc(Message& m)
       at System.Windows.Forms.ScrollableControl.WndProc(Message& m)
       at Telerik.WinControls.RadControl.WndProc(Message& m)
       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 SchedulerShamsiTest.Program.Main() in c:\Users\dyordano\Desktop\RadSchedulerFixPersianLocale (1)\SchedulerShamsiTest\Program.cs:line 19
  InnerException: 

Broken in version R3 2016 (2016.3.913)

How to reproduce:
SchedulerDayViewElement dayViewElement = (SchedulerDayViewElement)this.radScheduler1.ViewElement;
dayViewElement.SetColumnWidth(1, 2);

Workaround:
IDictionary cachedSum = (IDictionary)dayViewElement.GetType().GetField("cachedSum", BindingFlags.Instance | BindingFlags.NonPublic).GetValue(dayViewElement);
cachedSum.Clear();
IDictionary cachedColumnHorizontalOffset = (IDictionary)dayViewElement.GetType().GetField("cachedColumnHorizontalOffset", BindingFlags.Instance | BindingFlags.NonPublic).GetValue(dayViewElement);
cachedColumnHorizontalOffset.Clear();

SchedulerDayViewElement dayViewElement = (SchedulerDayViewElement)this.radScheduler1.ViewElement;
dayViewElement.SetColumnWidth(1, 2);

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.Month;
    
    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);
    this.radScheduler1.EnableExactTimeRendering = true;
    
}

Click "This month" in RadSchedulerNavigator.

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

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:

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");
    this.radScheduler1.Appointments.Add(appointment);
}

private void radCheckBox1_ToggleStateChanged(object sender, Telerik.WinControls.UI.StateChangedEventArgs args)
{
    this.radScheduler1.EnableExactTimeRendering = this.radCheckBox1.Checked;
}

Please refer to the attached gif file.

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

To reproduce:

public Form1()
{
    InitializeComponent();

    this.radScheduler1.ActiveViewType = SchedulerViewType.Day;
    RulerPrimitive ruler = (this.radScheduler1.SchedulerElement.ViewElement as SchedulerDayViewElement).DataAreaElement.Ruler;
    ruler.RangeFactor= ScaleRange.TenMinutes;
}

Workaround:

this.radScheduler1.GetDayView().RangeFactor = ScaleRange.TenMinutes;

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:

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;

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.

To reproduce:

public Form1()
{
    InitializeComponent();

    CultureInfo culture = new CultureInfo("en-US");
    culture.DateTimeFormat.FirstDayOfWeek = DayOfWeek.Monday;
    this.radScheduler1.Culture = culture;
    this.radScheduler1.ActiveViewType = Telerik.WinControls.UI.SchedulerViewType.Month;

    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);
}

Please refer to the attached gif file.

To reproduce:
Sub New() 
    InitializeComponent()

    Dim colors() As Color = {Color.LightBlue, Color.LightGreen, Color.LightYellow, Color.Red, _
        Color.Orange, Color.Pink, Color.Purple, Color.Peru, Color.PowderBlue}
    Dim names() As String = {"Alan Smith", "Anne Dodsworth", "Boyan Mastoni", "Richard Duncan", "Maria Shnaider"}
    For i As Integer = 0 To names.Length - 1
        Dim resource As New Telerik.WinControls.UI.Resource()
        resource.Id = New EventId(i)
        resource.Name = names(i)
        resource.Color = colors(i)
        Me.RadScheduler1.Resources.Add(resource)
    Next i
    Me.RadScheduler1.GroupType = GroupType.Resource
    Me.RadScheduler1.ActiveView.ResourcesPerView = Me.RadScheduler1.Resources.Count

    Me.RadScheduler1.ActiveViewType = SchedulerViewType.Timeline

    Dim rand As New Random
    For index = 1 To 20
        Dim a As New Appointment(DateTime.Now.AddDays(index), TimeSpan.FromHours(2), "A" & index)
        a.ResourceId = Me.RadScheduler1.Resources(rand.Next(0, Me.RadScheduler1.Resources.Count)).Id
        Me.RadScheduler1.Appointments.Add(a) 
    Next
    
    Dim timelineView As SchedulerTimelineView = Me.RadScheduler1.GetTimelineView()
     
    Dim oneMinute As New OneMinuteTimescale()
    timelineView.SchedulerTimescales.Add(oneMinute)

    oneMinute.Visible = True 
End Sub

Public Class OneMinuteTimescale
Inherits MinutesTimescale
    Public Overrides ReadOnly Property Name As String
        Get
            Return "OneMinuteTimescale"
        End Get
    End Property
    Public Overrides ReadOnly Property ScalingFactor() As Integer
        Get
            Return 1
        End Get
    End Property
End Class

Workaround: decrease the range: 

 timelineView.RangeStartDate = DateTime.Today
 timelineView.RangeEndDate = timelineView.RangeStartDate.AddDays(1)

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"));
 }
 

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 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

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;