dateModified is a property of article schema and related types in Schema.org. It holds the date and time of the last significant update to the content, usually alongside datePublished, written in a standard date format in JSON-LD.
Use it honestly. It should change when the content truly changes, such as corrected facts, new data or added sections, not when you fix a typo or change the layout. Search engines and AI tools compare it with the page and the XML sitemap, and a date that is bumped constantly without real edits erodes trust and gets ignored.
Show the same update date on the page where readers can see it, and keep the visible and structured dates in agreement. For topics that age quickly, a real, recent update date can help a page be considered current, which matters for AI citation and search ranking.
Related: Structured Data, Technical SEO.