You were taught that a period of time has a speed — that the fifties were slow and the world has accelerated. The foundation I work from says frequency is undefined at the boundary that sentence points at, so a period has no rate to have: a pace is an arithmetic done here, marks counted against a counter, both read in the present. That is why every century files the same complaint about acceleration, why two people in one hour honestly report opposite speeds, and why the decades most people file as slower are, on the measured ratio, the faster ones. … readWhat Is Pace