Datepicker question

Datepicker question

Dear :
how to write a jquery script to trigger anyother javascript function when i chagne a date
for example, when datepicker value is changed then trigger the test function and print the date value ,please help,thanks. 
 
<SCRIPT type=text/javascript>
 
$(function() {
  $("#datepicker").datepicker();
 });
 
 function test(day){
 alert("date is"+day");
}
 </SCRIPT>