$('month_selected').onchange = function(){
	      window.location = 'events.php?date='+$('month_selected').value+'&year='+$('year_selected').value ;
}

$('year_selected').onchange = function(){
      window.location = 'events.php?date='+$('month_selected').value+'&year='+$('year_selected').value;		
}