How far back in time could someone go and still be able to hold a conversation with someone in English?

by into_the_vast_cosmos
Seanzzxx

Not to discourage people from answering, but this is a very frequently asked question and here is a previous answer from the FAQ by /u/bloodswan : https://www.reddit.com/r/AskHistorians/comments/6q37mx/when_i_hear_chaucer_spoken_in_middle_english_it/dkuj8bw/