I wonder what determines the copyright year for a publication. I thought that the copyright year would be the same as the publication year, but seeing in (1)
put me in doubt (publication year: 2011; copyright year: 2012).
(1) Sutton, Charles, and Andrew McCallum. "An introduction to conditional random fields." Machine Learning 4.4 (2011): 267-373.
You are not showing the location of publication, however in the U.S., while Copyright is established the moment the work is created, the only effective way to claim infringement is to have registered the work with the U.S. Government's Copyright Office (http://www.copyright.gov). The date shown is more than likely the date that they received confirmation of the copyright registration from the office.
Subsequent editions will also refile copyright, so you can have various dates or a range of dates shown. On Molecular Biology of The Cell by Alberts, et.al, the copyright page has the 2015 copyright for the sixth edition but also lists the 2008 date for the preceding fifth edition.
I have generally seen date ranged copyrights on software, so if you select About This Mac on an Apple Mac computer, the splash screen shows (c) 1983 - 2015.
UPDATE
Even though copyright exists from the moment of creation of the work, an important reason for official registration has to do with the damages that you can seek for infringement. The following is from the Copyright Office's FAQ
Why should I register my work if copyright protection is automatic?
Registration is recommended for a number of reasons. Many choose to register their works because they wish to have the facts of their copyright on the public record and have a certificate of registration. Registered works may be eligible for statutory damages and attorney's fees in successful litigation. Finally, if registration occurs within five years of publication, it is considered prima facie evidence in a court of law. See Circular 1, Copyright Basics, section “Copyright Registration” and Circular 38b, Highlights of Copyright Amendments Contained in the Uruguay Round Agreements Act (URAA), on non-U.S. works.
It's a common thing for publishers to set the copyright date as late as possible so as to get an extra year of copyright protection. It's quite common to see books that appear in print in stores in the fall of one year (say 2012) bearing copyright dates in the next year (say 2013.) Apparently, if someone were to pirate the book during the period immediately after its appearance (say late in 2012) the copyright law allows the publisher to enforce the copyright. Generally, the publication year should be used in citations, CV's, etc. rather than the copyright year. If there is no publication date listed but there is a copyright date, then you should cite using the copyright date.
With journals, it's relatively common for issues to appear after the nominal date of the issue. Thus the December 2013 issue of the Journal of Tribble Biology might appear in February of 2014. Here, you cite based on the December 2013 date even though the issue didn't appear on time.
Dirty secret of the textbook publishing industry: many textbooks list a copyright date of the year after they are released. With US copyright protection lasting 70 years beyond the death of the author, they are not interested in a single extra year of copyright protection 100 years in the future (in many fields, textbooks are obsolete after a decade; even in fields where they are not they are replaced by new editions to break the used market). Rather, they seek to create the illusion that the book is recent. Instructors would rather use a 2014 book than a 2013 book, and pushing the copyright date forward is an easy way to gain a one year advantage on competitors.
The year of copyright is the year the work is created (if the published version is licensed), or the year of the transfer (when you sign over your rights). Journals can be behind schedule, so that a cover year can be any number of years behind the actual year of appearance.
Legally, the year of copyright is when the work was written. That can be very different from the publication year. Some texts have been buried in personal papers for many years after the death of the author, and only published posthumously.
