I was so confused when I was seeing posts 4 years old. “Old” isn’t even supposed to be an option lol.
Tested with other options, seems like TopWeek becomes TopDay, TopMonth becomes TopWeek, TopYear becomes TopMonth, and TopAllTime becomes TopYear.
So for now, you can enjoy seeing the creation of the Fediverse and read posts in reverse with this hidden option.
That’s a pretty cool bug! Looks like a classic off by one error.
Have you submitted it to GitHub? Here’s the repo.