By default, there are no creation dates associated with custom meta fields. If you check the description, you can see that it is a very simple table of key/value pairs associated with a post ID, plus an auto-increment field. There is no time component at all.
The only thing you can do with default functionality is get relative dates by checking the meta_id field. That is an auto-increment field which is incremented by one every time a new row is created. Lower numbers are always older than higher numbers, but there is not way to get a calendar date. If you need that functionality, you will need to create it yourself. I don’t think I understand what you want well enough to attempt code.