What file I have to change to edit the created date of an article from the front end? Using joomla 3.8.1.
Unfortunately, Joomla 3.x does not seem to allow the creation date to be modified from the front-end of the website.
The only third party extension I can find that enables this feature is EasyArticles which is a paid extension from StackIdeas. (You can verify this feature exists on their demo site).
There are probably other extensions that can do this and the Content Submission category in the JED might be a good place to start looking: https://extensions.joomla.org/category/authoring-a-content/content-submission