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Something could have been "created" 100 years ago, but only "Published" for the first time last month. I think datePublished is what you should use for articles, blog posts, etc... dateModified is also important for when you update the page to show it's fresh and needs to be re crawled and rendered. I wouldn't show any of them on the front end, though some people do prefer to see the Date Last Modified or Original Publish Date somewhere so they know if it's still relevant. It depends on the type of content you're publishing and if the topic moves quickly. If you want to provide the markup to search engines without showing it on the front end use JSON-LD.