One clear-cut way to get a grasp on the concept of then, now, some day is the division of data into two parts (this a paraphrasing of P.D. Ouspensky, Tertium Organum): our consciousness, and all that is not our consciousness. Through our senses, we perceive the other (cf. Soren Kierkegaard’s concept of “either/or” and Martin Buber’s explanation of “I and Thou”) and “organize” or “taxonomize” it by forming the concepts of time and space. That is, these concepts are in us, not in the universe—they are devices that our “selves” use to be able to perceive the Other with our senses. Of course, the book-length justification and explanation is much more sophisticated than this, but the simple answer to your question lies in this philosophical direction: Time does not “exist” in and of itself. It is simply a mental exercise of our minds that allows us to make sense of matter. As one pundit put it, “Without Time, everything would happen at once.” This view eliminates ideas of a "substance" or "property" of the universe called "Time."