From http://www.advancedcustomfields.com/resources/date-picker/

ACF date picker format

<?php

/*
*  Displaying single value
*/

?>
<p>Posted on: <?php the_field('date_picker'); ?></p>

<?php

/*
*  Create PHP DateTime object from Date Piker Value
*  this example expects the value to be saved in the format: yymmdd (JS) = Ymd (PHP)
*/

$date = DateTime::createFromFormat('Ymd', get_field('date_picker'));
echo $date->format('d-m-Y');

/*
*  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
}

/*
*  Format examples
*/

$js = "yymmdd"
$php = "Ymd"

$js = "dd/mm/yy"
$php = "d/m/Y"

$js = "yy_mm_dd"
$php = "Y_m_d"

?>