Function for customizing the Genesis post info function based on date post was published. For example the below function shows different post info for posts more than 6 months old. Adjust as required.

functions.php

<?php
// Don't copy opening PHP tag above

// Customize the post info function by date
add_filter( 'genesis_post_info', 'wsm_post_info_filter' );
function wsm_post_info_filter( $post_info ) {

	$post_date = the_date( 'Y-m-d','','', false );
	$date_limit = date( "Y-m-d", mktime(0,0,0,date("m")-6, date("d"), date("Y")) );

	$post_info = '';

	if ( $post_date > $date_limit ) {
		$post_info = '[post_date format="F j, Y"] [post_author before="<em>by</em> "] [post_comments zero="No Comments" one="1 Comment" more="% Comments"]';
	}
	else {
		$post_info = '[post_author before="<em>by</em> "] [post_comments zero="No Comments" one="1 Comment" more="% Comments"]';
	}
	return $post_info;
}