Query WP posts and weight recent posts more heavily

gistfile1.txt

//These are some params I've used elsewhere, may want to try adjusting
$date_scale = '5d';
$date_decay = 0.99999;
$date_origin = date( 'Y-m-d' );
$query = array(
	'query' => array(
		"function_score" => array(
			'query' => array( 'filtered' => array(
				'query' => array( 'multi_match' => array(
					'query' => $query,
					'fields' => array( 'content', 'title', 'tag.name', 'category.name', 'author' ),
					'cross_fields' => true, //look for each word in any field rather than all words in one field
					'operator' => 'and',
				) ),
				'filter' => $filter, //whatever filter you have
			) ),
			"functions" => array(
				array(
					'gauss'=> array(
						'date_gmt' => array(
							'origin' => $date_origin,
							'scale' => $date_scale,
							'decay' => $date_decay
						)
					)
				)
			),
			'score_mode' => 'multiply',
			'boost_mode' => 'multiply',
		) )
);