Comment by 1f60c

This might be specific to software, based on what the GNU project has to say about it[0], I think you should do it like this:

  Copyright 2014, 2016, 2017-2020

(Meaning the work was completed in 2014, a change was made to it in 2016 and every year from 2017 to 2020 was a "copyrightable year".)

[0]: https://www.gnu.org/licenses/gpl-howto.html#:~:text=The%20co...