Let’s say you have this situation (as I did). You are using a custom WordPress Post Type and you have set this custom post type to never publish. You’re using it as a way to save data using only the Dashboard, not ever publish the data to the theme. So the only save function you have is saving as a draft to protect it from public eyes.

Because of this situation the post’s date is always set to the modified date as it is never published. This caused a few issues for me as the application needed to pull up archives for posts based on the creation date, not the modified date.

But WordPress only gives the post a created date if it is published, so saving it as a draft updates post_date each time.

So, I had to prevent WordPress from updating post_date each time a draft was saved. I used the below to ensure that on drafts for a specific post type, here ihcrs_events, only got one post_date update when it was created, but needed to retain that date going forward.

https://gist.github.com/aubreypwd/c6109ed817ed89e232c3

As you can see we just update the post_date to the previous value using the wp_insert_post_data filter.

Note, pay extra careful attention to the priority of the filter, 99. This ensures the last update (there are many on save) retains the date. Using 10 or 20 will not retain the date.