This calculated field will return the creation date of the linked epic.
Create a new Calculated Date-Time Field (by JWT) custom field and name it appropriately.
Providing a description will help you to identify what the custom field does, but this step is optional.
Choose Date Time Picker
Add the field to the relevant view screens.
Remember: All calculated fields are read-only and cannot be manually updated on a create or edit screen.
Check the results
Once configured and added to an issue screen (e.g. for all stories), the result will look like this: