Are your sitemap dates telling the truth?
Crawlers use lastmod to decide what to recrawl. A future date, an invalid date, or one identical value across the whole site is worse than none. The crawler learns to ignore it.
Reads the lastmod values in your sitemap. Nothing is stored.
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How this check works
Shipwork reads /sitemap.xml, follows up to three child sitemaps when it is an index, and checks the lastmod values: are they valid dates, are any in the future, is one value reused across the whole site, and how old is the newest. Wrong values are worse than none.
What the sitemap lastmod checker reads
The check fetches /sitemap.xml from your site's origin and reads every lastmod value it contains. If the file is a sitemap index, it follows up to three child sitemaps and collects their lastmod values too. It records how many values it saw, how many are distinct and how old the newest one is.
Each value is parsed as a date. The check marks a value invalid if it cannot be parsed, and future if it is more than a day ahead of now. It also compares the set: if every URL shares one identical value, that is reported as a weak signal. It reads the dates, not the pages, so it cannot confirm that a date matches the last real edit.
How to read a lastmod result
A sane result means the dates parse, none are in the future, the values differ across URLs and the newest is recent. That is what makes lastmod useful to a crawler deciding what to recrawl. A clean result applies to the values in the sitemap the check could reach, including up to three child sitemaps when it is an index.
A future date is reported because crawlers treat it as unreliable and may then discount the rest of your dates. Invalid values are ignored by crawlers. One identical value on many URLs suggests the date is generated for the whole site rather than per page. A very old newest date suggests an abandoned sitemap. None of these prove a ranking change; they affect how eagerly a crawler returns.
Common causes and why they matter for search
Generators often stamp every URL with the build time, or with the time the sitemap was produced, which gives one value shared across the file. A migration can leave future dates, and hand-edited files can carry the wrong format. Once crawlers decide lastmod is not trustworthy, they fall back to other signals to schedule recrawls.
A truthful lastmod helps a crawler see that a product changed without waiting for an external signal. Wrong dates waste that hint. The value should reflect a meaningful change to the page, not a template change or a cache refresh, or the signal becomes noise that a crawler learns to ignore.
How to fix sitemap lastmod dates
Emit lastmod per URL from the page's real modification time. Use a valid datetime such as 2026-09-20 or 2026-09-20T10:00:00+00:00. If your platform cannot produce accurate per-page dates, omit lastmod rather than write one value for the whole site. Fix the generator, not the output file, so the next build stays correct.
On Shopify the sitemap is generated, so accurate dates depend on the platform; if they are wrong, omitting the element is better than a false signal. In WooCommerce, check the SEO plugin's sitemap settings and any caching layer that might stamp a fixed time. After a migration, replace future dates with real ones, then rerun the check.
When to use related sitemap checks
Use sitemap check when the file may not fetch or parse at all, and sitemap diff to see what changed between two crawls. Use freshness check when the question is whether your content reads as current, which lastmod alone cannot answer.
The content freshness article explains how recrawl hints and visible updates differ. For crawl scheduling on a store, see the Shopify sitemap guide.
Questions
What format should lastmod be?
Why is a future date a problem?
Should every URL have the same lastmod?
What format should sitemap lastmod use?
Why is a future lastmod a problem?
Should every URL share the same lastmod?
Does a correct lastmod improve rankings?
Which sitemaps does the check read?
Keep reading
What this reads
- Reads public pages from outside your network, the way a crawler does.
- No signup, and nothing is stored on the free checks.
- One of 83 checks across discovery, content, markup, trust and catalogue data.
Cool, just ran an audit and got some insights! Let’s see if I can fix them :)
Whoah! this site is crazy, nothing to roast at all
cool as heck, tried it on my blog and the insights it gave are helpful and not bluff.