can one deactivate the auto-dating?

You’d have to revise the query WordPress uses for your main loop.

If using the WordPress Default theme, you’d add this:
query_posts($query_string . ‘&orderby=category’)

just before this line in wp-content/themes/default/index.php:
<?php if (have_posts()) : ?>

See the template tag, query_posts(), for more orderby= parameters. Also check the order= parameter.

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