exclude a category only from monthly archives

I’m trying to modify archive.php to exclude a single category, but only from the monthly archive. I still want it to come up in category archives. Here’s the code I’ve currently got:

<?php get_header(); ?>

<div id=”left2″>
<?php is_tag(); ?>
<?php if (have_posts()) : ?>
<?php $post = $posts[0]; // Hack. Set $post so that the_date() works. ?>
<?php /* If this is a category archive */ if (is_category()) { ?>
<h2 class=”pagetitle”><?php single_cat_title(); ?></h2>
<?php /* If this is a tag archive */ } elseif( is_tag() ) { ?>
<h2 class=”pagetitle”>Posts Tagged ‘<?php single_tag_title(); ?>’</h2>
<?php /* If this is a daily archive */ } elseif (is_day()) { ?>
<h2 class=”pagetitle”>Archive for <?php the_time(‘F jS, Y’); ?></h2>
<?php /* If this is a monthly archive */ } elseif (is_month()) { ?>
<h2 class=”pagetitle”>Archive for <?php the_time(‘F, Y’); ?></h2>
<?php /* If this is a yearly archive */ } elseif (is_year()) { ?>
<h2 class=”pagetitle”>Archive for <?php the_time(‘Y’); ?></h2>
<?php /* If this is an author archive */ } elseif (is_author()) { ?>
<h2 class=”pagetitle”>Author Archive</h2>
<?php /* If this is a paged archive */ } elseif (isset($_GET[‘paged’]) && !empty($_GET[‘paged’])) { ?>
<h2 class=”pagetitle”>Blog Archives</h2>
<?php } ?>

<br/>
<?php while (have_posts()) : the_post(); ?>
<?php
$cat = get_the_category();
if ($cat[0]->cat_ID == 12)
continue;
?>
<div class=”post”>
<h3 id=”post-<?php the_ID(); ?>”>” rel=”bookmark” title=”Permanent Link to <?php the_title_attribute(); ?>”><?php the_title(); ?></h3>

<div class=”entry”>
<?php the_excerpt() ?>
</div>

<p><small><?php the_tags(‘Tags: ‘, ‘, ‘, ‘
‘); ?> Posted in <?php the_category(‘, ‘) ?> | <?php the_time(‘F j, Y’); ?> | <?php comments_popup_link(‘No Comments »’, ‘1 Comment »’, ‘% Comments »’); ?> <?php edit_post_link(“Edit”, “| “, “”); ?></small></p>

</div>

<?php endwhile; ?>
<p><?php next_posts_link(‘« Previous Entries’) ?> | <?php previous_posts_link(‘Next Entries »’) ?></p>

<?php else : ?>

<h2 class=”center”>Not Found</h2>
<?php include (TEMPLATEPATH . ‘/searchform.php’); ?>

<?php endif; ?>

<div class=”return”>|Return to top|</div>

</div>

<?php get_sidebar(); ?>

<?php get_footer(); ?>