How far back in time can you understand English? This site goes back by centuries allowing you to test yourself.
(www.deadlanguagesociety.com)
I got back to 1300 alright, but not 1200. But I had a bit of an odd upbringing - our houshold library for some reason had lots of British fiction from the 1700s/1800s and so I got a jump in obscure vocabulary. heh