As the data-binding documentation article
When embedding the RadTimePicker
control inside a data-bound control, use a data-binding expression to bind the value of the input control to the data source of the parent control. In addition to calling Eval
methods to perform data binding in a data-binding expression, you can call any publicly scoped code within the <%# and %> delimiters to execute that code and return a value during page processing.
This means that you can use custom code to provide a value for the control, but it does not have such properties as those of RadComboBox. This is expected since the RadDateInput control of the RadTimePicker allows only time input, not any kind of string. If you wish the time value look differently than it does in the datasource, you can use a format string to modify it through the DateFormat property of the DateInput.
the Telerik team