So three replies got deleted here. I suppose the reason people are finding this question difficult to answer is that to properly source an answer to this question you'd have to find and list a source that names a war for every year starting with 2013 and going back for several hundred years, perhaps several thousand. That's a lot of work!

Eventually, you'd find a year where the sources are rather thin, then you arbitrarily designate that as the last peaceful year. But all it would really tell you was that you got old enough that sources dry up.

I know somebody who did this parlour game, but it's not "AskHistorians" level information, so I won't post it. You can PM though if you care to hear such a dubious anecdote.