I thought most sites had the copyright year dynamically set to the current one, though I also kinda half recall someone saying that wasn't good practice either.
If I'm reading some content in the year 4023 that says (C) 2023 CM30, then I know the copyright has since expired and I'm free to do what I want with it. If it's dynamically saying (C) 4023 CM30 then it doesn't say when it was published.
If I'm publishing something in 2019 with a dynamic date, and it says (C) 2023 and by astonishing coincidence it's very similar to another piece of work by another author that has a static date and it says (C) 2021, it appears that my work post-dates their work rather than pre-dates it.
Mostly this matters much less now and there's other ways of proving publication date but in older media it mattered more.
Presumably if you know whether the author is alive or not, you'll be safe in knowing if it's under the copyright still, assuming it hasn't had a creative commons license attached or been put into the public domain.