Adding category to grid thumbnails?

hi all,

i found i nice options for adding a date to grid thumbnails
http://wordpress.org/support/topic/adding-date-to-grid-thumbnails?replies=7

.date-meta {
	background-color: #000;
	opacity: .5;
	filter: alpha(opacity=50);
	position: absolute;
	padding: 5px;
	top: 21px;
	right: 20px;
	color: #FFF;
}

function pinboard_post_thumbnail() {
	if( has_post_thumbnail() ) : ?>

		<figure class="entry-thumbnail">
            <div class="date-meta"><? echo get_the_time( get_option( 'date_format' ) );?></div>
			<a href="<?php the_permalink() ?>" rel="bookmark" title="<?php the_title_attribute(); ?>">
				<?php the_post_thumbnail( ( pinboard_is_teaser() ? 'teaser-thumb' : 'blog-thumb' ) ); ?>
			</a>
		</figure>
	<?php endif;
}

I try to change the code for adding the category but im to stupid to find it (no php expert)

can someone give me the solution plz?

thx

ps:sorry for my bad english 🙁