All file formats carry a "year" entry in their metadata for albums. What year are they talking about?

Is it the copyright year for your CD? Like when your particular cpoy was commerically released?
Is it the production year of your CD? Like the mastering date?
Is it the recording year of the song? Like when the artists recorded the thing?
Is it for the original album? Because your copy might be a re-release of the same album released as LP back in the 70s, or the old CDs released in the 80s.

Etc...

Thanks.

Usually, for me, when I apply a year to ID3V2 tags, it's the year the album (or particular version thereof), was released.

So, all albums released in 2008, would have "2008" in the Year field. Actually, I try to put the actual date of US release. So, "Year" would actually be something like "2008-04-10"

I do it that way, because software and devices that can't handle the full date, will usually then just read the first 4 characters, which in the yyyy-mm-dd format I use, is simply the year.