It's not if you don't keep track of releases. "Is Ubuntu codename 2 or 15 years old?" is basically unanswerable. even regular incrementing version numbers are easier: I don't keep track of Debian closely either, but I know "Debian 6" is pretty old, and Debian 12 or so is the latest version.

It's not easy to guess the release date. It's easy to tell if one name came before or after another though.