I hope you are doing well!
We just released the Latest Internal Build 2019.2.814 of the suite with a fix for this issue and wanted to notify you about that.
You can check the release notes at https://www.telerik.com/support/whats-new/aspnet-ajax/release-history/ui-for-asp-net-ajax-2019-2-814-(nightly-build-2019-08-14) as well as download the Telerik_UI_for_ASP.NET_AJAX_2019_2_814_Dev_hotfix.zip installation from https://www.telerik.com/account/product-download?product=RCAJAX.
<telerik:RadMonthYearPicker RenderMode="Lightweight" EnableTyping="true" ID="RadMonthYearPicker1" runat="server" EnableAriaSupport="true" TabIndex="1" > <DateInput ID="DateInput1" runat="server" EmptyMessage="Choose a date" ToolTip="Date input"> </DateInput> <ClientEvents OnPopupOpening="OnPopupOpening" OnPopupClosing="OnPopupClosing" /> <MonthYearNavigationSettings EnableScreenBoundaryDetection="true"></MonthYearNavigationSettings></telerik:RadMonthYearPicker><script> function OnPopupOpening(sender, args) { var popup = args.get_pickerControl().Popup; setTimeout(function () { var $popupElement = $telerik.$(popup.DomElement); $popupElement.find("tbody [role='gridcell'] a").eq(0).focus(); }); } function OnPopupClosing(sender, args) { sender.get_dateInput().focus(); }</script>var _onPopupOpening = function (sender, args) { setTimeout(function () { //TelerikDateTextBox and TelerikMonthYearTextBox have different interfaces. // get_pickerControl is for TelerikMonthYearTextBox // get_popupControl is for TelerikDateTextBox var popupDom = args.get_pickerControl ? args.get_pickerControl().Popup.DomElement : args.get_popupControl()._calendarDomObject; var $popupElement = $telerik.$(popupDom); //set focus to first "selected" element //$popupElement.find("tbody [role='gridcell'] a").eq(0).focus(); // Telerik's suggested selector... doesn't work because role is missing when EnableAriaSupport=false. $popupElement.find("tbody tr td.rcSelected a").eq(0).focus(); if (!$popupElement[0].classList.contains("hasTabEvent")) { $popupElement[0].addEventListener("keydown", function () { //set flag so we only setup event handlers one time. $popupElement[0].classList.add("hasTabEvent"); if (event.key === "Tab") { //we have to get the node list inside the listener, because it might have changed since the //calendar was opened. (Like if we changed the year or month in the calendar.) var $nodes = $popupElement.find("tbody tr td a"); //Some calendars have link buttons at the bottom. When present, we want to use the last button //as our last element instead of the last calendar entry. (See TelerikMonthYearTextBox) var $buttons = $popupElement.find(".rcButtons"); var first = $nodes[0]; var last = $buttons.length ? $buttons.children().last()[0] : $nodes.last()[0]; //If shift key down and current node is first, set target to last node. //If shift key up and current node is last, set target to first node. var target = event.shiftKey && event.srcElement.isSameNode(first) ? last : !event.shiftKey && event.srcElement.isSameNode(last) ? first : undefined; if (target) { target.focus(); event.preventDefault(); } } }); } }); //end setTimeout};