Post ordering problem with custom meta date

Hi,

I am writing a custom plugin for my client. It have to display some custom posts(event) on front page. Client want to order post according event date (custom meta field). I am using fallowing WP_Query.


$events=new WP_Query(
array(
'posts_per_page' => $postnum,
'post_type' => 'event',
'meta_key' => 'schedule_date',
'orderby' => 'meta_value',
'order' => 'ASC',
'tax_query' => array(
'relation'=>'AND',
array(
'taxonomy' => 'event_category', 'field' => 'id',
'terms' => $postcat
)
)

)
);

I am not getting desired result from this code. Client want to display latest upcoming event first. Event date (schedule_date) formatting like this 2nd-3rd June 2013.

Thank you in advance. Sorry if I could not explain problem properly.