Using the PublishPress plugin we will:

1. Go to the page/post/custom post.
2. Click New Revision.
3. Click Edit Revision.
4. Click on the post title. 
5. Make the desired changes.
6. Set the publish date/time.
7. Click save as draft. 
8. If the approve revision button does not highlight, refresh the page. 
9. Click Approve Revision. The revision will publish on the date and time you specified.