jQuery UI Datepicker. with Spring

HI I cannot resolve one things.

If Im using id of my input which is person.birthDate so this doesn work and the datepicker window doesnt show. (its meybe isue of javascript).

So I tried add class name, and the datepicekr window opend work fine, but if I click to date to confirm selection, so js ends with error.

elem is undefined

I tried with jquery 1.4 and 4.6.

Do you have some Idea to resolve it?

thank Petr form CZ