In many of my lectures and media interviews I regularly cite the observation that time is the only thing we measure against itself. We can only have a minute of a minute (unlike everything else in the known universe … for example weight of anything is defined in pounds, ounces, kilograms etc, distance is defined in feet, metres etc). This suggests to me that time is a totally subjective phenomenon. This is not an original observation …. for example philosopher J.C.C. Smart wrote the following in 1967 and it rings true to me: “If time flows … this would be a motion in reflect to hypertime. For motion in space is motion with respect to time, and motion of time or in time could hardly be a motion in time with respect to time … If motion in space is feet per second, at what speed is the flow of time? Seconds per what? Moreover, if passage is of the essence of time, it is presumably the essence of hyper-hypertime and so on ad infinitum.” …(Smart, J.C..C. “Time” in P. Edwards (ed), The Encyclopaedia of Philosophy. Collier MacMillan Page 126 (1967)