As of Q3 2011 RadTextBox provides support for the new HTML5 input types. To leverage this functionality you can use the InputType property of the control.
You can set to the following values:
Text - RadTextBox renders an input of type text and allows entering any type of string.
Number - RadTextBox renders an input of type number and only numbers are recognized as valid entry.
Date - RadTextBox renders an input of type date and lets the user enter only dates.
Time - RadTextBox renders an input of type time and lets the user enter only time.
DateTime - RadTextBox renders an input of type datetime and allows for specifying the time part of the DateTime object.
Note that not all browsers support HTML5 input types. Those
which do not recognize the new input types currently behave as if the
input is with type set to text.