AI Summary: Freshness is a consistency problem, not a date-stuffing tactic. Use datePublished and dateModified for accurate article history, sitemap lastmod for meaningful page changes, and HTTP Date or cache validators for their actual transport roles; none guarantees recrawl, ranking, or AI citation.
Keep four timestamps separate
datePublished answers when an article first became available. dateModified answers when its content was materially revised. Google documents both as ISO 8601 values for Article structured data and recommends using them when they accurately describe the page. [1]
Sitemap <lastmod> is a page-level publication hint. The Sitemap protocol says it should describe when the linked page was last modified, not when the sitemap was generated. [2] An HTTP Date header describes when the response was generated, while Last-Modified and ETag participate in HTTP caching. They are transport signals, not substitutes for editorial history.
A bundle rebuild or server timestamp refresh is not an article change. Update dates only when the answer changes, through the same release path.
Make freshness auditable
Keep the source of truth for publication and modification dates in the content record or CMS. Generate JSON-LD, visible bylines, sitemap entries, and any API representation from that record. Do not let a template print today’s date on every page. If a page is republished, preserve the original publication date and explain the modification where readers need that context.
| Signal | Meaning | Verify |
|---|---|---|
datePublished | First publication | Matches visible article history |
dateModified | Material editorial change | Matches the changed content |
<lastmod> | Linked page modification hint | Is not just build time |
Last-Modified | HTTP cache validator | Matches the representation served |
Date | Response generation time | Is not presented as editorial freshness |
Verification checklist
Change one paragraph in a test article and record expected dates. Fetch HTML, JSON-LD, sitemap XML, and headers before and after. Confirm only appropriate signals change, formats are valid, and a code-only release does not create a false editorial update.
Freshness becomes trustworthy when every timestamp has one job, one source of truth, and evidence behind it. It is a record of change, not a shortcut to visibility.