Not able to implement in Oracle Application Express 4.1

[kp4912gh]

I am not able to implement the datetimepicker/timepicker add-on on the Oracle Application Express 4.1 which is a database-centric web development framework of Oracle. Oracle APEX 4.1 already supports jQuery and I have included all necessary files required for the add-on to work. But it is not working!
When investigated with Firebug got a error in the jquery-ui-timepicker-addon.js script on line 932 which is as follows:

$t.datepicker($.timepicker._newInst($t, o)._defaults);

The error says:

$.timepicker._newInst is not a function

Please guide on what I am doing wrong.

Thanks & Regards,
Kiran