Allow users to easily edit the
field with a simple date picker field in admin. Allow users to edit and update this like any other field. Unless I'm missing something this currently requires customization. There are plugins like but these are related to scheduling rather than simply managing an existing publish date. I imagine most users expect the simple ability to manage publish date (or would utilize it) as a standard feature.
A simple example would be to back date a blog post. Below is a screenshot of this feature in WordPress.