datetimepicker is not a function jquery

Question

I working with datetimepicker jquery ui, when code below html , datetimepicker is not displaying and when i inspect with firebug console it displayed an error `

Answer 1

 $(document).ready(function(){
    $("#example1").datetimepicker({
      allowMultidate: true,
      multidateSeparator: ','
    });
 });