Order post by date with ACF

This comes directly from the ACF documentation:

/*
*  Order Posts based on Date Picker value
*  this example expects the value to be saved in the format: yymmdd (JS) = Ymd (PHP)
*/

$posts = get_posts(array(
    'meta_key' => 'custom_order', // name of custom field
    'orderby' => 'meta_value_num',
    'order' => 'ASC'
));

if( $posts )
{
    foreach( $posts as $post )
    {
        setup_postdata( $post );

        // ...

    }

    wp_reset_postdata(); // IMPORTANT - reset the $post object so the rest of the page works correctly
}