The <abbr>
element is not very useful to screen readers, even with the title
attribute.
The <time>
element is meant for machine-readable dates and offers nothing to the accessibility APIs.
These visual calendar grids should be tables (which allows column & row headers and table navigation commands).
The <time>
element is not an interactive control, so it should not have tabindex
; put it in a <button>
if you want it to take focus and it performs a function (or a link if it is meant to navigate).
If you want to support screen readers, the current date should use aria-current
.