Drafts publish with their initial creation date. This script shows a hint to update the publication date before you post the work.
When a previously saved draft is finally posted, AO3 uses the draft's initial creation date - which could be a month old - as the work's publication date. That's probably not what you wanted; you probably wanted the date when you hit the "Post" button.
This script adds a warning under the "Post" button. It also lets you set the Publication Date to today's date at the click of a button.

Thanks to @uncleasad for suggesting this script!