One SEO professional asked John Mueller during the submitted Question and Answer segment of his hangout about the last-modified date in their sitemaps.
Their question was: Our CMS automatically updates the last-modified date for every single change, even when adding a few words, fixing a spelling mistake, or adding an internal link.
Is this a good SEO practice? Or should the last-modified date only be updated when there are substantial changes made to the content?
John answered that he believes people do it in different ways. He does not think that from an SEO perspective, it matters all that much.
When Google looks at things like sitemap files, where there is also a last-modified date, the sitemap team ideally wants to see that date updated whenever there are any changes on the page – as it makes sense for Google to recrawl that page.
This includes things like a random link in the sidebar, for example. So from that perspective, people do it in different ways, and it should just work out regarding the last-modified date in the structured data itself. Usually, John believes it makes sense to have something aligned with when the primary content actually changes.
But, if there were technical reasons why you would have to do that immediately, or why your CMS does it immediately, John does not see a problem with that.
When it comes to dates on the page that Google sometimes shows in a snippet, what happens is they do try and find multiple mentions of that date on the page as a confirmation.
Then, Google uses that as something where they say “Well, this date is probably associated with this page. And because of this, we are fairly certain that it’s a reasonable date.” And if Google does show a date in this snippet, they would probably choose the one that’s most prominent on the page.
Google doesn’t show a date in the snippet for all pages, though. And it’s really something where you can help to guide that as well by making sure that perhaps there’s a visible date on the page also.
This happens at approximately the 41:35 mark in the video.