1) There is no element with the id or name as the value of the aria-controls attribute of the dateinput button with enabled ARIA support. 

2) The aria-valuemin and aria-valuemax attribute are not valid on role=textbox

To fix these, the following workarounds can be used

Option 1: OnClientLoad event of the DateInput element inside the DatePicker

function DatePickerOnClientLoad(sender) {
    setTimeout(function () {
        $telerik.$(sender.get_element()).parent().find("[role=button][aria-controls]").removeAttr("aria-controls");
        $telerik.$(sender.get_element()).removeAttr("aria-valuemin").removeAttr("aria-valuemax")
    })  
}

Option 2: using Sys.Application.Load event

function pageLoadHandler() {
    $telerik.$("[role=button][aria-controls]");
    $telerik.$("[role=textbox]").removeAttr("aria-valuemin").removeAttr("aria-valuemax");
    // Sys.Application.remove_load(pageLoadHandler);  
}
Sys.Application.add_load(pageLoadHandler);