Expiration
Most copyrights and patents have a finite term; when it expires, the work or invention falls into the public domain.
In most of the world, patents expire 20 years after they are filed.
Trademarks expire soon after the mark becomes a generic term.
Copyrights are more complex; generally, they expire in all countries except Guatemala, Mexico, Samoa and Colombia when all of the following conditions are satisfied:
- The work was created and first published before January 1, 1923, or at least 95 years before January 1 of the current year, whichever is later.
- The last surviving author died at least 70 years before January 1 of the current year.
- No Berne Convention signatory has passed a perpetual copyright on the work.
- Neither the United States nor the European Union has passed a copyright term extension since these conditions were last updated. (This must be a condition because the exact numbers in the other conditions depend on the state of the law at any given moment.)
These conditions are based on the intersection of United States and European Union copyright law, which most other Berne Convention signatories recognize.
Note that copyright term extension under U.S. tradition does not restore copyright to PD works (hence the