Although you only save an entry as a draft, the moment it was saved as a draft remains as its publish date for the rest of the entry's life. Making it so that when you actually post it to your blog, the date and time it appears to be posted on isn't the actual time it was posted on the blog, but the time it was published as a draft earlier.
How do you guys consider this? Should we be able to update the date if needed when turning drafts into blog posts?