Meta Query – between
$meta_query = array( 'relation' => 'AND', array( 'key' => 'festival_post_start_akce', 'value' => '$todaydate', 'compare' => '<=', 'type' => 'DATE', ), array( 'key' => 'festival_post_konec_akce', 'value' => '$todaydate', 'compare' => '>=', 'type' => 'DATE', ), );