IOW. A measurement. Keywords: measurement. Without a form of measurement (of change or geometry), time does not exist. I find this a curious concept, because it is circular reasoning. "Flowing" is a verb and by definition does work which is a mathematical function and should be measurable as a quantity of work done. It's completely arbitrary and it's better to say "time is an emergent by-product of "change". The definition of "flowing time" requires the assumption of a separate plenum, a 4th dimension (time) apart from the 3 Spatial dimensions , and containing a non-mathematical self-sustaining Temporal quality (Time) from which time can be borrowed for individual time-lines of change. But, of course, change is a purely mathematical function of a certain duration. All it needs is mathematical permission (Implicate) for it to become expressed in reality. This "requires and takes" time for completion of the change. But why MUST there be an available pre-existing (future) period of time for indeterminate change? Is there an answer to the question? It is impossible to measure time itself, because it it has do duration in and of itself, it is only a (timeless) permissive condition. Time as an emergent by-product of duration of change seems so much more elegant to me.