Sitemap lastmod that lies (and trains Google to ignore it)

Sitemap lastmod that lies (and trains Google to ignore it)

If your CMS stamps every URL in the sitemap with today's date on every regeneration, you've taught Google your lastmod is noise. After enough false signals, it stops trusting the field entirely — so even your genuinely updated pages lose their recrawl priority.

What lastmod does well when honest:
— Strong recrawl hint for pages that actually changed
— Cheap, scalable, no quota

Where it falls short:
— Zero value once Google flags it as unreliable
— No tool tells you it's been ignored; you just see slow recrawls

The fix: tie lastmod to real content-modified timestamps, not build time. If a page's body, title, or main entities didn't change, don't bump the date. Use ISO 8601 with timezone (2026-06-13T10:00:00+00:00), and audit a sample against your DB.

Best for: large sites with frequent partial updates.
Not for: setups that can't distinguish a real edit from a rebuild — better to omit lastmod entirely than fake it.