How to only show entries older than 12 months
You were close, you can set a postDate param on your craft.entries criteria model. And the Twig filter date_modify helps you to get the DateTime from 12 months ago.

{% set timeAgo = now|date_modify('5:00 -12 months') %}
{% set postDateParam = '&lt; ' ~ timeAgo|date('U') %}

{% set entries = craft.entries.section('news').postDate(postDateParam) %}