How to add Year to Twenty Fifteen theme footer

Copy the footer.php page from the Twenty Fifteen theme to the Twenty Fifteen child theme folder

<?php
/**
* The template for displaying the footer
*
* Contains the closing of the "site-content" div and all content after.
*
* @package WordPress
* @subpackage Twenty_Fifteen
* @since Twenty Fifteen 1.0
*/
?>

</div><!-- .site-content -->

<footer id="colophon" class="site-footer" role="contentinfo">
<div class="site-info">
<?php
/**
* Fires before the Twenty Fifteen footer text for footer customization.
*
* @since Twenty Fifteen 1.0
*/
do_action( 'twentyfifteen_credits' );
?>
<a href="<?php echo esc_url( __( 'http://example.com/', 'twentyfifteen' ) ); ?>"><?php printf( __( '&copy; 2015 %s', date( "Y" ), 'twentyfifteen' ), 'Example' ); ?></a>
</div><!-- .site-info -->
</footer><!-- .site-footer -->

</div><!-- .site -->

<?php wp_footer(); ?>

</body>
</html>