Custom Column for date book is added to the library?

Sometimes I want to browse by the oldest in my library or browse what was added during a specific time frame, but the default #date column changes if I download metadata or count pages/words, and so forth, and #last_modified changes if I update anything else.

This seems like a basic database feature (when was this book first acquired?) but I confess I haven't been able to find an answer. How would I do this so I could browse books I bought during the holiday season two years ago?