Create custom post order (with custom post type meta)

Save your data in a single field as either YYYY-MM-DD or UNIXTIME. Then query like this:

$args = array(
    'post_type' => 'POST_TYPE_NAME',
    'meta_key' => 'date-key-name',
    'orderby' => 'meta_value',
    'order' => 'ASC',
);
$query = new WP_Query( $args );

You should get an order, unless I am having a bad morning, of Day -> Month -> Year, which I believe is what you want. I don’t have your data at hand so I can’t actually test that.

Related

https://wordpress.stackexchange.com/a/75318/21376

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