--- title: " invalid, in the future, or identical across entries (seo/sitemap-lastmod)" description: "seo/sitemap-lastmod: Google uses lastmod only if it is consistently accurate; lastModified: new Date() stamps every URL with the build time, so Google learns…" canonical: https://void-design.vercel.app/rules/seo/sitemap-lastmod lastModified: 2026-09-16 --- # invalid, in the future, or identical across entries `seo/sitemap-lastmod` · severity **warn** · category SEO · detected by `void seo` and `void audit` ## Why it matters Google uses lastmod only if it is consistently accurate; lastModified: new Date() stamps every URL with the build time, so Google learns to ignore it. ## How to fix it Use each page's real content-modified date (from CMS or git) in W3C Datetime format. ## References - https://developers.google.com/search/docs/crawling-indexing/sitemaps/build-sitemap#additional-notes-about-xml-sitemaps - https://developers.google.com/search/blog/2023/06/sitemaps-lastmod-ping ## More seo rules `void seo` reports 60 rules in this category. What search engines need from the raw response: status codes, titles and descriptions in , self-referencing canonicals, one h1, crawlable links, Open Graph, icons, robots.txt and a sitemap with real dates. - `robots-sitemap-directive` robots.txt has no absolute Sitemap: line — [seo/robots-sitemap-directive](https://void-design.vercel.app/rules/seo/robots-sitemap-directive) - `sitemap-missing` No reachable sitemap — [seo/sitemap-missing](https://void-design.vercel.app/rules/seo/sitemap-missing) - `sitemap-invalid` Sitemap isn't valid sitemap XML or exceeds protocol limits — [seo/sitemap-invalid](https://void-design.vercel.app/rules/seo/sitemap-invalid) - `sitemap-url-invalid` Sitemap is relative or on another host — [seo/sitemap-url-invalid](https://void-design.vercel.app/rules/seo/sitemap-url-invalid) - `sitemap-url-status` Sitemap lists URLs that don't return 200 directly — [seo/sitemap-url-status](https://void-design.vercel.app/rules/seo/sitemap-url-status) - `sitemap-url-not-indexable` Sitemap lists noindex, robots-blocked or non-canonical URLs — [seo/sitemap-url-not-indexable](https://void-design.vercel.app/rules/seo/sitemap-url-not-indexable) - `duplicate-title` Multiple pages share the same — [seo/duplicate-title](https://void-design.vercel.app/rules/seo/duplicate-title) - `duplicate-description` Multiple pages share the same meta description — [seo/duplicate-description](https://void-design.vercel.app/rules/seo/duplicate-description) Detected by `void seo` and `void audit`. Explain it in a terminal: `void rules seo/sitemap-lastmod`