Better copyright

 // http://www.wpbeginner.com/wp-tutorials/how-to-add-a-dynamic-copyright-date-in-wordpress-footer/
function synth_copyright() {
	global $wpdb;
	$copyright_dates = $wpdb->get_results("
		SELECT
		YEAR(min(post_date_gmt)) AS firstdate,
		YEAR(max(post_date_gmt)) AS lastdate
		FROM
		$wpdb->posts
		WHERE
		post_status = 'publish'
	");
	$output = '';
	if($copyright_dates) {
		$copyright = "© " . $copyright_dates[0]->firstdate;
		if($copyright_dates[0]->firstdate != $copyright_dates[0]->lastdate) {
			$copyright .= '-' . $copyright_dates[0]->lastdate;
		}
		$output = $copyright.' - Site r&eacute;alis&eacute; par <a href="https://synth.agency" target="_blank">synth.agency</a>';
	}
	return $output;
}