I'll take that. Whenever the first year was, I'm betting there was no war.
There you go, if it didn't exist it could've have happened.
You make it sound as if we're only talking about war on Earth. Granted a long time ago in a galaxy far far away there was a fair bit of war.
Anyways, at a time where time existed and war was not a concept. There was a time where there was no war. If that time lasted a year, job done.
In a Biblical sense, how long did it take for Adam and Eve to fuck things up in the Garden of Eden?