Based on the information below, I understand having a datePublished for the actual post on the WordPress blog index page, but it required a datePublished for the actual blog.
How does Google treats the datePublished at the LiveBlogPosting level (not the liveBlogUpdate level)?
Is it the date that the blog was published? Is it the date of the most recent post that was published? Is it the last date the blog was modified? Or maybe something else?
From Schema.org’s perspective:
The datePublished property for the LiveBlogPosting gives the publication date of the blog post, i.e., when it was first published, typically saying "something happened" and then the live blogging begins.
The datePublished property for each BlogPosting referenced with the liveBlogUpdate property gives the publication date of that update.
Both have nothing to do with the date of the last modification. This can be given in the dateModified property:
For the LiveBlogPosting you could use dateModified each time another update gets posted, but that would be redundant (as it would be the same date as the datePublished of the newest update). I would only use it for modifications that happen after the live blogging stopped.
For the referenced BlogPosting items, you could use dateModified if the update, after it got published, gets modified (but that’s probably rather uncommon, as typically a new update gets posted with a correction instead).
From Google’s perspective, it wouldn’t make any sense not to follow Schema.org’s definitions. However, they don’t seem to have a Rich Snippet (or similar product) that makes use of LiveBlogPosting (or do they?).
