In specific environmental conditions related to the culture settings, RadDateTimePicker can't change its selected date upon user selection.

The sender of the KeyPress event should be RadMaskedEditBox. Currently, it is RadMaskedEditBoxElement.

The TabStop property set via the property builder of VS should be able to set the determine the tabbing behavior of RadTextBox and more specifically, the behavior of its inner TextBoxItem. Right now, the developer has to use a line of code to determine this behavior:
this.radTextBox1.TextBoxElement.TextBoxItem.TabStop = false;
while the TabStop of RadTextBox is always false, so that the focused can be always transferred to the inner TextBoxItem.

When the ReadOnly property of RadTimePicker is true, setting the Value property in code does not cause any effect on the UI of RadTimePicker.

Users should be able to insert the decimal separator character of the current culture by pressing the '.' (dot) char from the numeric pad.

RadMarkupDialog should provide the possibility to be localized by a localization providers.

It will be nice if there is a TextAlign property at control level for RadMaskedEditBox.

There should be a TextAlign property at RadMaskedEditBox contorl level

A nice addition to our RadTextBox will be the ability to add an autocomplete mode supporting multiple choinces, just like in the "To" textbox in Outlook.

RadMaskedEditBox should be able to handle dynamic masks. The core of this feature is the ability to have a value for the number of allowed characters on one hand and a value for the number of maximum characters on the other hand.

One should be able to pick and type only the time portion of a datetime value.

Add a possibility to suggest misspelled words if they are all capital letters or contains numbers.

Workaround:
((RadDateTimePickerCalendar)this.dtpFromTaarich.DateTimePickerElement.GetCurrentBehavior()).Calendar.Navigating +=
               new CalendarNavigatingEventHandler(dtp_Navigating);
 
void dtp_Navigating(object sender, Telerik.WinControls.UI.CalendarNavigatingEventArgs e)
       {
           if (e.Direction == Telerik.WinControls.UI.CalendarNavigationDirection.Forward)
           {
               if (!e.IsFastNavigation)
                   e.StartDate = (sender as RadCalendar).CalendarElement.View.ViewStartDate.AddMonths(-1);
               else
                   e.StartDate = (sender as RadCalendar).CalendarElement.View.ViewStartDate.AddMonths(-12);
           }
           else if (!e.IsFastNavigation)
           {
               e.StartDate = (sender as RadCalendar).CalendarElement.View.ViewStartDate.AddMonths(1);
           }
           else e.StartDate = (sender as RadCalendar).CalendarElement.View.ViewStartDate.AddMonths(12);
       }

Resolution: You need to set the RightToLeft property to Yes of CalendarBehavior
RadDateTimePickerCalendar calendarBehavior = this.radDateTimePicker1.DateTimePickerElement.GetCurrentBehavior() as RadDateTimePickerCalendar;
RadCalendar calendar = calendarBehavior.Calendar as RadCalendar;
calendar.RightToLeft = System.Windows.Forms.RightToLeft.Yes;

RadTimePicker/RadTimePickerElement should display empty text or Null text if the Value property is set to null.

Workaround:
        Me.RadTimePicker1.NullText = "Please, enter a time!"
        Me.RadTimePicker1.Value = Nothing
        Me.RadTimePicker1.TimePickerElement.MaskedEditBox.TextBoxItem.Text = ""

Fix: RadMaskedEditBox MaskedType Numeric Mask "D" allows to enter only one digit
Workaround: Change RadMaskedEditBox Mask from "D" to "D0"

RadDateTimePicker/RadDateTimePickerElement should display empty text if the Value property is set to null.

It's not possible to set using code not UI the RadTimePicker.Value when RadTimePicker.ReadOnly = true

Unable to write DateTimePicker/RadMaskedEditBox day part when Culture is set to "tr-TR"

FIX. When we change the Culture property, the control will display the current date even if the value of the control is NULL

Workaround:
Set an empty string to the Hosted TextBox control after the Culture set.
For example:
radDateTimePicker1.Culture = Thread.CurrentThread.CurrentCulture;
radDateTimePicker1.DateTimePickerElement.TextBoxElement.TextBoxItem.HostedControl.Text = "";

Workaround: Users should use a N0 mask instead of G mask.