Time seems to be a fundamental concept which we have to accept as a precondition of our understanding of our own life and the whole universe around us. … Even if we cannot provide a formal definition of time, something instructive and important about time can always be said concerning how it is related to other fundamental concepts like space, event, thing, causation, free will and human experience.[1]
[1] Jan Faye. Perspectives on time. Boston: Kluwer, 1997: p. 1.