Typically HN posts have the following info in small type below the post title:
# points,
username of author,
time elapsed since submitting,
flag this post,
# comments.
Then there's these that I see once in a while that only show the time elapsed since the story was submitted.
A screenshot of what I'm talking about:
http://imgur.com/qWD71
2 comments
Ask HN: How do some posts on HN only show the posted time? | Heykuki News