How to display last 20 posttitles with dates?

Not sure how to get the last 5 or 20, but this is how I managed to display titles and authors:
<li id="catpost-<?php the_ID(); ?>">" rel="bookmark" title="Permanent Link: <?php the_title(); ?>"><?php the_title(); ?>

<?php the_author() ?> ~ <?php the_date(''); ?> at <?php the_time() ?>
I’m using it on my category pages. I thought having category pages displaying every post we’ll ever have in that category; seemed better to simply have a list of links on the category page.
http://developedtraffic.com/category/web-news/