Meta search dates
$meta_query = array( 'relation' => 'AND', array( 'key' => 'dnl_event-start_time', 'value' => 'start', 'compare' => '>', 'type' => 'DATETIME', ), array( 'key' => 'dnl_event-start_time', 'value' => 'end', 'compare' => '<', 'type' => 'DATETIME', ), );