import type { SitemapItem } from '../index.js';
/**
 * Returns the most recent `lastmod` among the given sitemap items as an
 * ISO 8601 string, or `undefined` when none of them carry a valid `lastmod`.
 *
 * Used to stamp each `<sitemap>` entry in the sitemap index with the freshest
 * date present in the child sitemap it points to, so search engines can tell
 * which child sitemaps actually changed without refetching all of them.
 */
export declare function getLatestLastmod(items: SitemapItem[]): string | undefined;