Custom field date input messes up sorting

My WP template is getting together slowly but surely, mainly because of the fantastic resources out there!

I have a custom post type called ‘events’ that I use to display events on my index page, as well as on a specific agenda page. I use the custom fields ‘location’, ‘date’ and ‘time’. Obviously, I want my events to be sorted on date. However – the format I’m using is like this: 2nd February 2012 etc.

Loop code

<?php query_posts( 'post_type=events&posts_per_page=4&meta_key=datum&orderby=meta_value&order=ASC'); ?>
    <?php if(have_posts()) : ?><?php while(have_posts()) : the_post(); ?>

Output code

<?php
$date = get_post_meta($post->ID, 'datum', true);
if ($date){
echo $date;
}
?>

Within a month my events are sorted OK. However as soon as an event enters from the next months, it will only look at the number for sorting. I need to find a way to convert my date (or to enter a date) so that WordPress sorts the posts on a different date-formatting compared to what is outputted…..But so far, I haven’t been able to do that with my custom-fields. I tried a lot of tutorials, but they all use a different time-formatting.

Anyone has suggestions that might solve this small but significantly annoying problem?