Reversing the order of items in a category rss feed?

Question

Is there an easy way to reverse the default item order of a category rss feed?

Default: Last posted item first
Wanted: First posted item first

No plugins please, plain wp api function calls (such as add_action or add_filter) will do!

Answer 1

In your functions.php file

function reverseorder($query_string)  
{
    return query_posts( $query_string . '&order=ASC' );
}
add_action( 'rss2_head', 'reverseorder' );

EDIT

GET parameters on RSS feed
cat - category ID (e.g. 23)
author - author ID (e.g. 14)
year - year the post was published (e.g. 2007)
day - day of the month the post was published (e.g. 17)
monthnum - number of the month the post was published (e.g. 6)
hour - hour of the day the post was published (e.g. 23)
minute - minute of the hour the post was published (e.g. 48)
second - second of the minute the post was published (e.g. 51)
p - the unique post ID to display (e.g. 629)
paged - specific page number as displayed on the main blog page (e.g. 3)

Answer 2

You can simply reorder you RSS Feed via the GET parameter ?order=ASC or ?order=DESC after your FEED url!