Cacher is the code snippet organizer for pro developers

add_action( 'pre_get_posts', 'sortbyACFpre_get_posts' );
function sortbyACFpre_get_posts($query) {
// do not alter the query on wp-admin pages and only alter it if it's the main query
if (!is_admin() && $query->is_main_query()){
	if ( is_home() ){
		$query->set('meta_query', array(
		    'relation' => 'OR',
		    array(
		        'key' => 'fecha_inicio',
		        'compare' => 'NOT EXISTS',
		    ),
		    array(
		        'key' => 'fecha_inicio',
		        // 'value' => date("Ymd", time()),
		        'compare' => 'EXISTS',
		    ),
		));
		$query->set('orderby', array(
		    'meta_value_num' => 'DESC',
		    'date' => 'DESC',
		));
	}
}