The public domain consists of all works that never had copyright protection and works that no longer have copyright protection. The public domain also includes most works created by the United States government.
Therefore, anyone may reproduce, redistribute, or adapt the work and there is no longer a need to seek permission for its use.
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