How long copyright lasts

Copyright subsists for a variety of lengths in different jurisdictions, with different categories of works and the length it subsists for also depends on whether a work is published or unpublished. In most of the world the default length of copyright for many works is generally the life of the author plus either 50 or 70 years. Copyright in general always expires at the end of the year concerned, rather than on the exact date of the death of the author. (The right to reclaim a copyright--or "terminate the transfer" of a copyright--commences and ends on the anniversaries of exact dates in the United States.)
So when can one conclude that a book is in the public domain? In the United States, all books and other works published before 1923 have expired copyrights and are in the public domain. In addition, works published before 1964 that did not have their copyrights renewed 28 years after first publication year also are in the public domain, except that books originally published outside the US by non-Americans are exempt from this requirement, if they are still under copyright in their home country