Order by custom post meta date

I’m trying to order my upcoming events by custom post meta date, but it’s not working as it should. It orders by days only and ignores months and years.
example:

1st April 2016
4th July 2016
10th May 2016

<?php
global $post;

 $today = date('jS F Y');
    $args = array(
            'post_type'         => 'event',
            'posts_per_page'    => 4,
            'meta_key'          => 'start_date', 
            'orderby'           => 'meta_value_num',
            'order'             => 'DESC',
            'meta_value_num'    => $today,
            'meta_compare'      => '>'
  );

$loop = new WP_Query( $args );

echo '<ul class="events-list">';
    while ( $loop->have_posts() ) : $loop->the_post(); 
echo '<li>';
echo '<div class="meta-fields">';
$start_date = get_post_meta( get_the_ID(), 'start_date', true );
$new_format_start = date_i18n('jS F Y',strtotime($start_date)); 
$end_date = get_post_meta( get_the_ID(), 'end_date', true ); 
echo  $new_format_start;

    if ($end_date) {
    $new_format_end = date_i18n('jS F Y',strtotime($end_date)); 
    echo ' - ' . $new_format_end;
    } else {
    echo "";
    } 
echo '</div>';
?>
<p><a href="<?php the_permalink(); ?>"><?php the_title(); ?></a></p>

<div class="entry-content">
     <p class="event-widget"> <?php echo get_the_excerpt(); ?> </p>
</div>
</li>

<?php 
    endwhile;
    echo '</ul>';
    }