I don't know how you're using the CSV file, but if you're importing it to Memento or probably anywhere else, the creation date of all imported entries become the date it was created during import, I believe, so yes, if you select the Info option on an imported entry, it will probably show the date of import.
To preserve it, I would create a Date or DateTime field for it, and set its default to the current date & time. If you never update it, that date & time will never change. If the risk that it could change is bothersome to you, you could, instead of using the default, set it with a CreatingTheEntry trigger, BeforeSavingTheEntry trigger with the following script in the trigger...
entry().set("Creation date", Date.now().getTime());
This script will run only when creating the entry.