kradblatt_date_regular
$meta_query = array( 'relation' => 'AND', array( array( 'key' => 'kradblatt_date_regular', 'value' => 'on', 'compare' => '=', ), ), );
$meta_query = array( 'relation' => 'AND', array( array( 'key' => 'kradblatt_date_regular', 'value' => 'on', 'compare' => '=', ), ), );