Log in as admin. Create a few events for upcoming days in future. Load up a page which has calendar mini block. Straight after page load inspect page source code and make sure the <a> tag displaying the date elements doesn't have any "aria-controlls" attribute. Check this for date with no events, current date, and a future date with events. Mouse over current date, make sure <a> tag for the date now has a "Aria-controls" attribute pointing to the panel div. Mouse over any date without any events, make sure the td tag for the date does not have any "Aria-controls" attribute associated. Mouse over any other date with events, make sure <a> tag for the date now has a "aria-controls" attribute pointing to the panel div. Install chrome extension https://chrome.google.com/webstore/detail/accessibility-developer-t/fpkknkljclfencbdbgkenhalefipecmb and run the tool on a freshly loaded page and make sure the test "ARIA state and property values must be valid" passes. PS:- There are some rendering issues with the mouseover panel, those are not related to this fix.