1. Create a post for your Blogger blog as usual
2. Click on the Post Options link found at the bottom left corner of the Compose box and directly above the Publish Post button
3. Set the specified date and time you wish your post to be published on
4. Click on the Publish Post button
If you have set a retrospective date your post will be published immediately and you will be able to view it in your blog archives.
If you set a future date your post will be scheduled for publication. Click on the link to Edit Posts and view your post in the list. It should be at the top of the list. Notice that it will marked "scheduled" in red. When the exact date and time set is arrived at Blogger will publish your post automatically.
In this tutorial I have discussed reasons why you might choose to set your own user defined post date for your Blogger posts. I have also shown you how to go about setting a different post date through the Post Options feature in Blogger.