We add the current year to the copyright dates, the current updates are protected from the time of authorship. So if the copyright says, 2012, 2014, 2022; I would add a 2024. The commit records can be used to determine what was changed each instance, but the update provides notice of when changes were made.
Discerning what is protectable creative expression versus functional and therfore unprotected is an issue for the courts.