jQuery UI datepicker: Configure keyboard shortcuts

This is not configurable through datepicker. You would have to change the _doKeyDown method source here.

The easiest way to do this would be to extend the widget. It would look something like this:

$.extend($.datepicker, {
     _doKeyDown: function(event){
           //copy original source here with different
           //values and conditions in the switch statement
     }
});