Garbage in, garbage out. If you look up ‘hansenerd’, they’re at https://shoddy.site/@cg - where it shows they joined in 2042.

Lemmy’s backend should probably be the one to sanitise it rather than each app.

This is intended behavior—instance admins can manually change account creation dates in the database, including to dates in the future, which leads to some funny account ages. We plan to implement some custom handling for these cases, but since they’re quite rare it’s not a development priority right now.