This is best accomplished by adding a custom Blog Post metafield definition. You can add this in the Settings area of your shop admin under “Metafields.” Set the field up as follows:
From there, you will just need to add the liquid code to your template. How you choose to do this is up to you, but this code should be what you need to process and format the entered date/time. Just make sure it is used in a place where the “article” object is accessible
Storing the metadata with the post will only just store data with it, it won’t re-arrange the posts in the blog feed or render the custom date unless you modify the theme’s liquid code.