Which day/year will world violence end?

The day mankind is obliterated from the planet. Bam...world peace.

Our poor world has been plagued with violence since it's beginning and I don't think it will ever end. Wish I could give you a real answer but I just don't think mankind will ever get along.

Only after ALL life has been eradicated.

Alas, violence will be with us as long as humankind exists. (Animals are violent too, of course, but I doubt that you were asking about them.)

It all started with Cain, confound the man, when he took up a gibber and clobbered Abel. And since the First Family set the example the rest of us have followed suit.

Or course, since we're made in God's image I suppose violence is inevitable. Look what he did to Sodom and Gomorrah, look what he did to the Egyptians, look what he did to Sennacherib and his cohorts. If we were created with an inbuilt inevitability for violence, how can we avoid it?

Case in point, John 8:7. Jesus preached love and forgiveness but when he tried to save the woman taken in adultery with those immortal words, "Whoever is without sin among you, let him be the first to cast a stone at her,"  he was shocked when a middle-aged woman picked up a rock and bounced it of the poor girls head. He sighed and said, "You just don't get it, do you, Mum?"