Google Advises Removing Lastmod Dates When They're Unreliable or Incorrect
TLDR
Google's Gary Illyes says sites are better off omitting lastmod dates in XML sitemaps entirely if those dates are incorrect or unreliable.
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Optimixed's original report on this story.
Gary Illyes from Google advised on Bluesky that websites should skip lastmod dates in their XML sitemaps if the dates are inaccurate, noting it also saves bytes. Per SERoundtable, Illyes was responding to a question about whether sites with unreliable lastmod dates would perform worse than those with none at all. Google reiterated existing guidance that lastmod dates should only be updated for significant content changes, not routine updates or copyright notices, and warned against using them as an SEO manipulation tactic.