Which years to write into copyright header?

Question

How should I write the years in the copyright header?

Just firstyear, every year like firstyear, ..., currentyear, the range firstyear-currentyear or just the last currentyear?

For example, I currently work on code I wrote in 2011, and it just says Copyright 2011 in the header.

Answer 1

I believe that you should write the year (or the range of years) that you developed the code in. Copyrights expire after some time, the value you enter is used to determine that time.

Updated:

There is some nice information on this subject on Wikipedia here http://en.wikipedia.org/wiki/Copyright.

Typically, the duration of copyright is the whole life of the creator plus fifty to a hundred years from the creator's death, or a finite period for anonymous or corporate creations. Some jurisdictions have required formalities to establishing copyright, but most recognize copyright in any completed work, without formal registration.

"Copyright", followed by the year of the first publication of the work and the name of the copyright holder. Several years may be noted if the work has gone through substantial revisions.

Answer 2

I think the dates should reflect the year(s) the content was worked on, however some shops want the compile date in your source code comments.