I once read that one way to look at relativity is that everything is always moving at the speed of light but normally objects mostly move in the time dimension. In this case the rate of passage of time would be in metres per second!--King DJ
You know, you could actually usefully use this as a measure of acceleration at relativistic speeds. --Vitenka
ISTR GeneralRelativity? implies things like the ClocksParadox?, where this value would be other than one (in which case it is SecondInReferenceFrameAPerSecondInReferenceFrameB? or something like that) --Bobacus