You will get all completed orders of today in wordpress / woocommerce store.
$today = date('Y-m-d');
$args = array(
'post_type' => 'shop_order',
'post_status' => 'wc-completed',
'posts_per_page' => -1,
'date_query' => array(
array(
'column' => 'post_date',
'after' => $today,
'before' => $today,
'inclusive' => true,
),
),
);
$orders = get_posts($args);