It is confounding at times to differentiate between a phenomenon and our human perception of a phenomenon.. this, I think, is inevitable. Our perception of time is indeed quite relative to us, the observers. But, if we did not exist to observe the universe, would what we're calling time still exist?
We quantify our observation of time as a measurement, but in reality, the universal phenomenon we are observing isn’t that measurement. So I believe
time would exist independent of our observation.
I think that the universal phenomenon of time is change relative to the speed of light. Why the speed of light? Because, as Einstein predicted in his Relativity theory, the speed of light is the universal constant which all other movement is ultimately relative to. I think the passage of time is the relative relationship between a phenomenon traveling slower than light-speed to that which is traveling at light-speed. In order to experience the passage of time, one must be traveling slower than the speed of light, because if one is traveling at speed, then there is no relative difference between their movement and the overall speed of the universe. A thing subject to time is literally being
passed by other elements of the universe that are traveling at light-speed.
Something that's always fascinated me is the Lorentz Transformation (
http://physics.about.com/od/relativisticmechanics/a/relativity_3.htm). The Twin Paradox thought experiment based on this equation reveals something very telling about the nature of time. Basically, it indicates if you were to travel at the speed of light, there would be no passage of time for you. What does this really say?.. I think it's telling us that time is indeed change or movement, but that it is ultimately defined by the top-speed that exists in this universe.
Something else indicated by the theory of Relativity is that space and time are two measurements of the same thing. It seems reasonable to me to see space as the placement of matter relative to other matter - it is ultimately the relationship between elements. Time, then, would be the speed at which these relative relationships change in comparison to the speed of light - the speed at which the overall universe is expanding.
It seems that the nature of our universe is indeed quite relative, not only due to our observation of it, but due to the way its existence relies upon the relationship between things.