The year in a copyrigt notice is supposed to be the year when the work was first published. So updating just the year would technically be wrong. That said, it

The year in a copyrigt notice is supposed to be the year when the work was first published. So updating just the year would technically be wrong. That said, it doesn’t matter much since the notice is purely informational - it doesnt actually alter the copyrigt of the work. If you want the notice to protect against infringing, surely you want to state the earliest year possible. But some read the notice as “page last updated” in which case you want it as recent as possible. But why not just write “last updated…” then?