WP_Query with previous_posts_link() and next_posts_link( - wordpress

Question

I'm working on an archive page for my website. I've created a page with an archive template and I'm using WP_Query to get the posts that match certain variables. I use the following code:
$myposts = new WP_Query(array('author'=>$writer,'m'=>$date, 'cat'=>$category, 'posts_per_page'=>5)); ?>
and
<?php if($myposts->have_posts()){
while ( $myposts->have_posts() ) {
$myposts->the_post();
include 'article-box.php';
}
} ?>
where 'articles.php generates the posts. Then comes the part which doesn't work.
<div id="pages-nav">
<div class="alignleft"><?php previous_posts_link('« Previous Articles') ?></div>
<div class="alignright"><?php next_posts_link('Next Articles »','') ?></div>
</div>
The links for the next / previous pages don't show up at all. Is this to do with the fact that I use a page with archive template or is there anything else I'm missing?
If I enter
[http://localhost/wordpress/archives/page/2/?date=201307&category=5&writer=0&submit=search]
as URL I get the next posts as it should be with the "Previous" link but not the "Next" link
Edit:
print_r($myposts) returns:
WP_Query Object ( [query_vars] => Array ( [author] => 0 [m] => 201307 [cat] => 7 [posts_per_page] => 5 [paged] => 1 [error] => [p] => 0 [post_parent] => [subpost] => [subpost_id] => [attachment] => [attachment_id] => 0 [name] => [static] => [pagename] => [page_id] => 0 [second] => [minute] => [hour] => [day] => 0 [monthnum] => 0 [year] => 0 [w] => 0 [category_name] => carolynne [tag] => [tag_id] => [author_name] => [feed] => [tb] => [comments_popup] => [meta_key] => [meta_value] => [preview] => [s] => [sentence] => [fields] => [menu_order] => [category__in] => Array ( [0] => 7 [1] => 10 [2] => 11 [3] => 12 [4] => 54 ) [category__not_in] => Array ( ) [category__and] => Array ( ) [post__in] => Array ( ) [post__not_in] => Array ( ) [tag__in] => Array ( ) [tag__not_in] => Array ( ) [tag__and] => Array ( ) [tag_slug__in] => Array ( ) [tag_slug__and] => Array ( ) [ignore_sticky_posts] => [suppress_filters] => [cache_results] => 1 [update_post_term_cache] => 1 [update_post_meta_cache] => 1 [post_type] => [nopaging] => [comments_per_page] => 50 [no_found_rows] => [order] => DESC ) [tax_query] => WP_Tax_Query Object ( [queries] => Array ( [0] => Array ( [taxonomy] => category [terms] => Array ( [0] => 7 [1] => 10 [2] => 11 [3] => 12 [4] => 54 ) [include_children] => [field] => term_id [operator] => IN ) ) [relation] => AND ) [meta_query] => WP_Meta_Query Object ( [queries] => Array ( ) [relation] => ) [post_count] => 5 [current_post] => -1 [in_the_loop] => [comment_count] => 0 [current_comment] => -1 [found_posts] => 22 [max_num_pages] => 5 [max_num_comment_pages] => 0 [is_single] => [is_preview] => [is_page] => [is_archive] => 1 [is_date] => 1 [is_year] => [is_month] => 1 [is_day] => [is_time] => [is_author] => [is_category] => 1 [is_tag] => [is_tax] => [is_search] => [is_feed] => [is_comment_feed] => [is_trackback] => [is_home] => [is_404] => [is_comments_popup] => [is_paged] => [is_admin] => [is_attachment] => [is_singular] => [is_robots] => [is_posts_page] => [is_post_type_archive] => [query_vars_hash] => 5d9c9d82fe6cd2bec72ca33ab10482e7 [query_vars_changed] => [thumbnails_cached] => [query] => Array ( [author] => 0 [m] => 201307 [cat] => 7 [posts_per_page] => 5 [paged] => 1 ) [request] => SELECT SQL_CALC_FOUND_ROWS wp_posts.ID FROM wp_posts INNER JOIN wp_term_relationships ON (wp_posts.ID = wp_term_relationships.object_id) WHERE 1=1 AND YEAR(wp_posts.post_date)=2013 AND MONTH(wp_posts.post_date)=07 AND ( wp_term_relationships.term_taxonomy_id IN (7,10,11,12,56) ) AND wp_posts.post_type = 'post' AND (wp_posts.post_status = 'publish' OR wp_posts.post_status = 'private') GROUP BY wp_posts.ID ORDER BY wp_posts.post_date DESC LIMIT 0, 5 [posts] => Array ( [0] => WP_Post Object ( [ID] => 43393 [post_author] => 1013 [post_date] => 2013-07-31 18:17:44 [post_date_gmt] => 2013-07-31 17:17:44 [post_content] => This film is a cross [...]

Answer 1

Send $paged variable to query as like below:
$paged = (get_query_var('paged')) ? get_query_var('paged') : 1;
$myposts = new WP_Query(array('author'=>$writer,'m'=>$date, 'cat'=>$category, 'posts_per_page'=>5,'paged' => $paged));
And change your pagination code to below:
<div id="pages-nav">
<div class="alignleft">
<?php previous_posts_link('« Previous Articles',$myposts->max_num_pages); ?>
</div>
<div class="alignright">
<?php next_posts_link('Next Articles »',$myposts->max_num_pages); ?>
</div>
</div>