add_filter( 'aioseo_sitemap_rss', 'aioseo_filter_rss_sitemap_entries' );

function aioseo_filter_rss_sitemap_entries( $entries ) {

	$entries = array_map( function ( $entry ) {

		if ( empty( $entry['pubDate'] ) ) {

			return $entry;

		}

		$dateTime = new DateTime();

		$dateTime->setTimestamp( strtotime( $entry['pubDate'] ) );

		$dateTime->setTimezone( new DateTimeZone( 'Europe/Moscow' ) );

		$entry['pubDate'] = date_format( $dateTime, 'D, d M Y H:i:s O' );

		return $entry;

	}, $entries );

	return $entries;

}