The chart is based in part on Laura N. Gasaway's chart, "When Works Pass Into the Public Domain," at <http://www.unc.edu/~unclng/public-d.htm>, and similar charts found in Marie C. Malaro, A Legal Primer On Managing Museum Collections (Washington, D.C.: Smithsonian Institution Press, 1998): 155-156.  A useful copyright duration chart by Mary Minow, organized by year, is found at <http://www.librarylaw.com/DigitizationTable.htm>.  A "flow chart" for copyright duration is found at <http://www.bromsun.com/practice/copyrights/copyright_durations.html>.  See also Library of Congress Copyright Office. Circular 15a, Duration of Copyright: Provisions of the Law Dealing with the Length of Copyright Protection (Washington, D.C.: Library of Congress, 2004) <http://www.copyright.gov/circs/circ15a.pdf>.

² All terms of copyright run through the end of the calendar year in which they would otherwise expire, so a work enters the public domain on the first of the year following the expiration of its copyright term.  For example, a book published on 15 March 1923 will enter the public domain on 1 January 2019, not 16 March 2018 (1923+95=2018).  

³ Unpublished works when the death date of the author is not known may still be copyrighted, but certification from the Copyright Office that it has no record to indicate whether the person is living or died less than 70 years before is a complete defense to any action for infringement.  See 17 U.S.C. § 302(e).

⁴ Presumption as to the author's death requires a certified report from the Copyright Office that its records disclose nothing to indicate that the author of the work is living or died less than seventy years before.

⁵ "Publication" was not explicitly defined in the Copyright Law before 1976, but the 1909 Act indirectly indicated that publication was when copies of the first authorized edition were placed on sale, sold, or publicly distributed by the proprietor of the copyright or under his authority.”

 ⁶ Not all published works are copyrighted.  Works prepared by an officer or employee of the United States Government as part of that person's official duties receive no copyright protection in the US.  For much of the twentieth century, certain formalities had to followed to secure copyright protection.  For example, some books had to be printed in the United States to receive copyright protection, and failure to deposit copies of works with the Register of Copyright could result in the loss of copyright.  The requirements that copies include a formal notice of copyright and that the copyright be renewed after twenty eight years were the most common conditions, and are specified in the chart.  

⁷ A 1961 Copyright Office study found that fewer than 15% of all registered copyrights were renewed. For books, the figure was even lower: 7%.  See Barbara Ringer, "Study No. 31: Renewal of Copyright" (1960), reprinted in Library of Congress Copyright Office. Copyright law revision: Studies prepared for the Subcommittee on Patents, Trademarks, and Copyrights of the Committee on the Judiciary, United States Senate, Eighty-sixth Congress, first [-second] session. (Washington: U. S. Govt. Print. Off, 1961), p. 220.  A good guide to investigating the copyright and renewal status of published work is Samuel Demas and Jennie L. Brogdon, "Determining Copyright Status for Preservation and Access: Defining Reasonable Effort," Library Resources and Technical Services 41:4 (October, 1997): 323-334.  See also Library of Congress Copyright Office, How to investigate the copyright status of a work. Circular 22. [Washington, D.C.: Library of Congress, Copyright Office, 2004].  The Online Books Page FAQ, especially "How Can I Tell Whether a Book Can Go Online?" and "How Can I Tell Whether a Copyright Was Renewed?", is also very helpful.

⁸ The following section on foreign publications draws extensively on Stephen Fishman, The Public Domain: How to Find Copyright-free Writings, Music, Art & More. (Berkeley: Nolo.com, 2004).  It applies to works first published abroad and not subsequently published in the US within 30 days of the original foreign publication.  Works that were simultaneously published abroad and in the US are treated as if they are American publications.

⁹ Foreign works published after 1923 are likely to be still under copyright in the US because of the Uruguay Round Agreements Act (URAA) modifying the General Agreement on Tariffs and Trade (GATT).  The URAA restored copyright in foreign works that as of 1 January 1996 had fallen into the public domain in the US because of a failure to comply with US formalities.  One of the authors of the work had to be a non-US citizen or resident, the work could not have been published in the US within 30 days after its publication abroad, and the work needed to still be in copyright in the country of publication.  Such works have a copyright term equivalent to that of an American work that had followed all of the formalities.  For more information, see Library of Congress Copyright Office, Highlights of Copyright Amendments Contained in the Uruguay Round Agreements Act (URAA). Circular 38b. [Washington, D.C.: Library of Congress, Copyright Office, 2004].

¹⁰ US formalities include the requirement that a formal notice of copyright be included in the work; registration, renewal, and deposit of copies in the Copyright Office; and the manufacture of the work in the US.

¹¹ The differing dates is a product of the question of controversial Twin Books v. Walt Disney Co. decision by the 9th Circuit Court of Appeals in 1996.  The question at issue is the copyright status of a work only published in a foreign language outside of the United States and without a copyright notice.   It had long been assumed that failure to comply with US formalities placed these works in the public domain in the US and, as such, were subject to copyright restoration under URAA (see note 9).  The court in Twin Books, however, concluded "publication without a copyright notice in a foreign country did not put the work in the public domain in the United States."  According to the court, these foreign publications were in effect "unpublished" in the US, and hence have the same copyright term as unpublished works.  The decision has been harshly criticized in Nimmer on Copyright, the leading treatise on copyright, as being incompatible with previous decisions and the intent of Congress when it restored foreign copyrights.  The Copyright Office as well ignores the Twin Books decision in its circular on restored copyrights.  Nevertheless, the decision is currently applicable in all of the 9th Judicial Circuit (Alaska, Arizona, California, Hawaii, Idaho, Montana, Nevada, Oregon, Washington, and Guam and the Northern Mariana Islands), and it may apply in the rest of the country.

¹² See Library of Congress Copyright Office, International Copyright Relations of the United States. Circular 38a. [Washington, D.C.: Library of Congress, Copyright Office, 2004].

¹³ See 63 Fed. Reg.19,287 (1998), Library of Congress Copyright Office, Copyright Restoration of Works in Accordance With the Uruguay Round Agreements Act;  List Identifying Copyrights Restored Under the Uruguay Round Agreements Act for Which Notices of Intent To Enforce Restored Copyrights Were Filed in the Copyright Office.