That is the date code for the service life of the part. Mainly issued because of the treated paper that acts as the filtering substrate. Supposedly depending on storage conditions like temperature and moisture that can break down rending the filter less effective, or ineffective. Based on how long fuel filters last, not sure how much stock I put in that. Or maybe I just don't replace mine enough lol.
One day Just bought it from ebay. Don't know how long the person had it.
I guess once you use it the date doesn't matter anymore. It must be a warning before use.
Stuff like that is also partly due to the lawyer happy society we live in, and companies covering their butts. There are expiry dates on child seats, bike helmets, etc. I would inspect the condition, maybe compare to a new one, and go from there. Or if it's a PITA to install, might just be worth it to get another so you don't have to worry about it.