What Causes A Year?

A year is the name mankind has given to the ( annual) elliptical path of our earth around our very own star--the sun. When we say that other planets take, say two years to revolve around the sun ,we do so in earthly terms, that is measure other planetary rotations by the earthly year.. If we had lived on another planet we would have divided time up differently, according to that planets time taken to do one complete path around our parent star, plus its daylight hours, seasons etc etc. Aileeny