Do the dates in my sitemap tell crawlers what changed?
The last-modified date beside each address in your sitemap tells a crawler which pages to fetch again, but only when it is true. We check that the dates are there, that they are in the standard format, that none is in the future, and that they are not all one date.
What it actually is
We read the sitemap at its standard address, which the scan has already fetched, and look at the optional last-modified date on each entry. A good sitemap carries it for most entries, writes it in the standard date format, never dates a page in the future, and shows different dates for pages that changed on different days. A sitemap larger than we fetch is judged on the part we hold. A sitemap kept at another address is not read by this check.
Why it matters
The sitemaps standard defines the date as when the page last changed, not when the sitemap was produced. A crawler that learns the dates are honest can skip what has not moved and return quickly to what has. A crawler that learns every page claims to have changed today stops believing the field, and Google says it uses the date only when it proves consistently accurate. Honest dates make a re-visit cheaper for the machine and surer for you.
What good looks like
Each entry carries the date its page last changed in the standard format, set by the content system when a page is edited, and the dates differ as the pages do. A page that has not changed keeps its old date.
Being honest about it
The date is optional in the standard, so leaving it out is allowed, and we are only reporting that it cannot help a machine then. We cannot see when a page really changed, so we cannot tell a true date from a plausible one: we catch the visible mistakes, which are dates that cannot be read, dates in the future and one date repeated across a large sitemap. The check only passes or warns, and because it is new it sits under measured, not scored: it never moves your score.
Where most sites go wrong
A sitemap generator that stamps every address with the moment it ran, so every page claims to have changed on the day of the last build. The other is a date written in a local format such as day, month and year with slashes, which is not the standard format and cannot be read.
On the web
State of the Web · November 2026In November 2026, 52% of the sites where it applies (2% of the sites we could read) passed the “Sitemap dates tell a machine what changed” check.
Not enough history yet.
Based on the sites Bot Appétit has scanned. Most of these sites come from lists we scan for research. Not a random sample of the web.
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