I'm guessing the answer lies in my functions.php file, and has something to do with this:
$date = sprintf( '<a href="%1$s" title="%2$s" rel="bookmark"><time class="entry-date" datetime="%3$s" pubdate>%4$s</time></a>', esc_url( get_permalink() ), esc_attr( get_the_time() ), esc_attr( get_the_date( 'c' ) ), esc_html( get_the_date() ) );
But I'm stuck on how to get the same effect. Any help would be appreciated.
Also, to achieve this in Twenty Twelve, is it enough to just edit that one file? Previously, I had to edit my index.php, single.php, etc.