What I have tried:
I tried attaching displayParams on the field in edit view to try to detect the change with
'updateCallback' => 'yourCustomFunction(this);',
But to no avail.
Regular approaches that work with text fields like attaching an event listener as in:
field_name.addEventListener('change', yourCustomFunction, false);
Also fail. It simply never picks up the change.
Seemingly trivial task, but completely stuck at this point, my only solution is to track every click on the screen and
check the before and after value of the date field. But this is extremely inefficient.