Next.js says 'hydration failed' on my v0 landing page

You found it. Anything that differs between server and browser at render time (dates, Math.random, window) causes this. The year usually matches, but a timezone edge or a cached HTML from last year does not.

Either render it on the client only:

const [year, setYear] = useState<number>();
useEffect(() => setYear(new Date().getFullYear()), []);

or hardcode the year in a constant you bump once a year. For a footer I'd hardcode it.