DO YOU START typing out a post or an idea that you either don’t finish or plan to finish later? As you know they end up in the ‘Drafts’ section of your WordPress. The problem is, when you finish the post and publish it, the date and time from when you first began creating the post is the time reference that WordPress uses to publish the piece.
An illustration: I create a post on May the 13th. But I don’t publish it until May 18th. Any posts you have made in between these dates that DID get published, will still be ahead of the ‘New’ post.
The simplest solution is to copy paste your material into a New Post and publish, that way it publishes to the top of your blog and more importantly your post will be published to WordPress Reader as a new post. If you publish a post that was once a draft it will not appear as a new post in the Reader and less people will see it. I hope that helps.