Updating copyright year
Alternatively, put a notice at the beginning saying which file it is generated from. To update the list of year numbers, add each year in which you have made nontrivial changes to the package.
(Here we assume you’re using a publicly accessible revision control server, so that every revision installed is also immediately and automatically published.) When you add the new year, it is not required to keep track of which files have seen significant changes in the new year and which have not.
It is recommended and simpler to add the new year to all files in the package, and be done with it for the rest of the year.
If a file has been explicitly placed in the public domain, then instead of a copyright notice, it should have a notice saying explicitly that it is in the public domain.It might be in the file, or it might be displayed when the program starts up.