How do i search post by jquery datepicker?

I think it’s better to use date_query as argument, like so :

$query = new WP_Query( 'year=2012&monthnum=12&day=12' );

or:

$args = array(
    'date_query' => array(
        array(
            'year'  => 2012,
            'month' => 12,
            'day'   => 12,
        ),
    ),
);
$query = new WP_Query( $args );

Source : https://codex.wordpress.org/Class_Reference/WP_Query