Blogger Quirks ?
I think blogger has some quirks. When you make a post which you drafted at an earlier date, the draft date comes up in the post and not the date at which you make the post.
Time to file bug report ?
Update: There is indeed a workaround where you can change the date in "Post Options". However, I still feel that the date of the post must be the date when you actually make the post and not the date that you drafted it !
Posted by Shyam Krishnaswamy at 2:23 PM