Can dateModified be unset on a Schema.org Article, if so when should it be set for the first time?

Question

I am trying to understand what the various dates mean in Article from Schema.org.

From what I can understand is the following:

• dateCreated is when the writer first starting with the article. Nothing has been made public yet for reading. dateCreated can be earlier or the same as datePublished, but not later.
• datePublished is when the writer is finished with the article and has made it available online for reading.
• dateModified is when the article is modified.

The above is my opinion. What is the general opinion regarding this?

If an article has not be edited will it then contain nothing/null for dateModified? The reason why I ask is because when you run your code through the structured data testing tool it says that dateModified is not required but recommended. How can it be recommended for articles that have not been edited from their original source? Should dateModified then be the same as datePublished just so that the red error message can go away? Or shouldn't I worry about it and treat it as a warning?

When is dateModified set for the first time? After dateCreated or after datePublished?

Answer 1

Personally, I would omit the dateModified property as long as the article is not modified after publication. However, that’s more of a philosophical decision than a technical one. Consumers should be able to handle it both ways if they are inclined to do so:

• If datePublished == dateModified: The article was never modified after publication (or it was modified, but the author didn’t update the dateModified value).
• If no dateModified: The article was never modified after publication (or it was modified, but the author didn’t provide the dateModified property).

Google doesn’t give more information in their Article Rich Snippet documentation, but in their Top Stories with AMP documentation, they say (bold emphasis mine):

The date and time the article was most recently modified, in ISO 8601 format. If the article has never been modified, you can omit this property or use the same date as datePublished.

I guess it’s safe to assume that they will handle it in the same way for their other search result features (e.g., the Article Rich Snippet), too.

Answer 2

dateModified always has a potential value (there's always something you could set) and can be equal to or later than dateCreated. ‘Creating is modifying’ and a good example of this is the filesystem on whatever OS you're using — creating a file sets the dateCreated and the dateModified together, then subsequent edits change the dateModified.

Whether or not you count publishing as a modification or not is up to you, but I encourage you to be consistent with this. In my case, I do count publishing as a modification, so when publishing I set datePublished and update dateModified.