hi! you may be interested in this post from the FAQ

• What is the longest span of time the world has gone without a war?

here are a few posts that expand/explain a bit more, but with the same conclusion: not enough records exist to be able to derive an answer

• When was the last time the world was at peace? Posted earlier to /r/askreddit and someone suggested I post it here... makes sense.

• Has there ever been world peace at any point in History or have we always been at war?

• I saw somewhere where the amount of years the world has seen total peace was less than 100 years, can anyone prove that correct or refute it?

• Was there ever a time when the world was at relative peace?