The only solution that works without hacking jquery ui is to add an event listener to the mousedown event of the year drop down:, eg

$(document.body).delegate('select.ui-datepicker-year', 'mousedown', function(){

var select = $(this);

var opts = select.children().get();

if ($(opts).first().val() < $(opts).last().val()){

select.empty().html(opts.reverse());

}

});