How to fix hAtom errors reported in Google Webmaster Tools?

Google Webmaster Tools reports a bunch of structured data error: Missing: author, Missing: entry-title and Missing: updated for all my pages. For my posts thoug, it’s only Missing: updated.

I’m using WordPres CM with a custom theme based on the Twenty Thirteen theme. Pretty much every thread I’ve enountered on this issue tells me to edit my single.php file and add the entry-title class to the h1 tag containing the_title. However, my single.php file looks like this:

<?php
/**
 * The template for displaying all single posts
 *
 * @package WordPress
 * @subpackage Twenty_Thirteen
 * @since Twenty Thirteen 1.0
 */

get_header(); ?>

    <div id="primary" class="content-area">
        <div id="content" class="site-content" role="main">

            <?php /* The loop */ ?>
            <?php while ( have_posts() ) : the_post(); ?>

                <?php get_template_part( 'content', get_post_format() ); ?>
                <?php twentythirteen_post_nav(); ?>
                <?php comments_template(); ?>

            <?php endwhile; ?>

        </div><!-- #content -->
    </div><!-- #primary -->

<?php get_sidebar(); ?>
<?php get_footer(); ?>

I don’t know PHP very well, but I guess that the following line

            <?php get_template_part( 'content', get_post_format() ); ?>

means that it’s loading the file content.php, which looks like this:

<?php
/**
 * The default template for displaying content
 *
 * Used for both single and index/archive/search.
 *
 * @package WordPress
 * @subpackage Twenty_Thirteen
 * @since Twenty Thirteen 1.0
 */
?>

<article id="post-<?php the_ID(); ?>" <?php post_class(); ?>>
    <header class="entry-header">
        <?php if ( has_post_thumbnail() && ! post_password_required() && ! is_attachment() ) : ?>
        <div class="entry-thumbnail">
            <?php the_post_thumbnail(); ?>
        </div>
        <?php endif; ?>

        <?php if ( is_single() ) : ?>
        <h1 class="entry-title post-title"><?php the_title(); ?></h1>
        <?php else : ?>
        <h1 class="entry-title post-title">
            <a href="<?php the_permalink(); ?>" rel="bookmark"><?php the_title(); ?></a>
        </h1>
        <?php endif; // is_single() ?>

        <div class="entry-meta">
            <?php twentythirteen_entry_meta(); ?>
            <?php edit_post_link( __( 'Edit', 'twentythirteen' ), '<span class="edit-link">', '</span>' ); ?>
        </div><!-- .entry-meta -->
    </header><!-- .entry-header -->

    <?php if ( is_search() ) : // Only display Excerpts for Search ?>
    <div class="entry-summary">
        <?php the_excerpt(); ?>
    </div><!-- .entry-summary -->
    <?php else : ?>
    <div class="entry-content">
        <?php
            /* translators: %s: Name of current post */
            the_content( sprintf(
                __( 'Continue reading %s <span class="meta-nav">&rarr;</span>', 'twentythirteen' ),
                the_title( '<span class="screen-reader-text">', '</span>', false )
            ) );

            wp_link_pages( array( 'before' => '<div class="page-links"><span class="page-links-title">' . __( 'Pages:', 'twentythirteen' ) . '</span>', 'after' => '</div>', 'link_before' => '<span>', 'link_after' => '</span>' ) );
        ?>
    </div><!-- .entry-content -->
    <?php endif; ?>

    <footer class="entry-meta">
        <?php if ( comments_open() && ! is_single() ) : ?>
            <div class="comments-link">
                <?php comments_popup_link( '<span class="leave-reply">' . __( 'Leave a comment', 'twentythirteen' ) . '</span>', __( 'One comment so far', 'twentythirteen' ), __( 'View all % comments', 'twentythirteen' ) ); ?>
            </div><!-- .comments-link -->
        <?php endif; // comments_open() ?>

        <?php if ( is_single() && get_the_author_meta( 'description' ) && is_multi_author() ) : ?>
            <?php get_template_part( 'author-bio' ); ?>
        <?php endif; ?>
    </footer><!-- .entry-meta -->
</article><!-- #post -->

I assume this is the key part:

<div class="entry-meta">
                <?php twentythirteen_entry_meta(); ?>
                <?php edit_post_link( __( 'Edit', 'twentythirteen' ), '<span class="edit-link">', '</span>' ); ?>
            </div><!-- .entry-meta -->

where

            <?php twentythirteen_entry_meta(); ?>

is calling a function from the functions.php file:

if ( ! function_exists( 'twentythirteen_entry_meta' ) ) :
/**
 * Print HTML with meta information for current post: categories, tags, permalink, author, and date.
 *
 * Create your own twentythirteen_entry_meta() to override in a child theme.
 *
 * @since Twenty Thirteen 1.0
 */
function twentythirteen_entry_meta() {
    if ( is_sticky() && is_home() && ! is_paged() )
        echo '<span class="featured-post">' . esc_html__( 'Sticky', 'twentythirteen' ) . '</span>';

    if ( ! has_post_format( 'link' ) && 'post' == get_post_type() )
        twentythirteen_entry_date();

    // Translators: used between list items, there is a space after the comma.
    $categories_list = get_the_category_list( __( ', ', 'twentythirteen' ) );
    if ( $categories_list ) {
        echo '<span class="categories-links">' . $categories_list . '</span>';
    }

    // Translators: used between list items, there is a space after the comma.
    $tag_list = get_the_tag_list( '', __( ', ', 'twentythirteen' ) );
    if ( $tag_list ) {
        echo '<span class="tags-links">' . $tag_list . '</span>';
    }

    // Post author
    if ( 'post' == get_post_type() ) {
        printf( '<span class="author vcard"><a class="url fn n" href="%1$s" title="%2$s" rel="author">%3$s</a></span>',
            esc_url( get_author_posts_url( get_the_author_meta( 'ID' ) ) ),
            esc_attr( sprintf( __( 'View all posts by %s', 'twentythirteen' ), get_the_author() ) ),
            get_the_author()
        );
    }
}
endif;

SO, here’s the big question:

What do I need to change to fix those structured data errors?

Any help is very much appreciated.