Scheduled posts are published with the modified_date of when you wrote the post and the post_date of when it was published. For a non-scheduled post the modified_date and post_date are the same when the post is published.
What happens when you use the push-button installation of WordPress from your site’s cPanel and then, for whatever reason, forget your username and the (unique?) password you used? Simple, right? You just click on the “Lost your password?” link from your site’s log in page and there you go; but, what if you never set up … ∞