This is filed in the "new to me" category. I assume it's not new to the vibrant SEO forum community which I find all to easy to ignore. Oops.
This is triggered when your search query includes a past date. It's interesting to note that Google notes whether a subscription is required or not. That's not something that you tend to see in Google News onebox. Why not? Probably because there are enough subscription free stories for news articles by the time a story is large enough to make the onebox.