materializecss date-picker protractor (Error: Element is not clickable at point )

Im trying to use date-picker similar to bithdate of(http://ift.tt/1P4j7Fn) and have a separate directive for it.

I tried following command

$('aria-owns="birthdate_root"').click();
 browser.sleep(5000);
$('data-pick="1451845800000"').click();

but failed and found error Element is not clickable at point

Any help is much appropriated....Thanks in advance