下記で解決しました。
<dl>
<?php
global $post;
$args = array( 'posts_per_page' => 5, 'category' => 10 );
$myposts = get_posts( $args );
foreach ( $myposts as $post ) :
setup_postdata( $post ); ?>
<dt><?php the_time('Y.m.d');?><span><?php
$cats = get_the_category();
foreach($cats as $cate):
if($cate->parent) echo $cate->cat_name;
endforeach;
?></span></dt><dd id="post-<?php the_ID();?>"><a href="<?php the_permalink()?>"><?php the_title();?></a></dd>
<?php endforeach;
wp_reset_postdata(); ?>
</dl>
