Jim Kelley wrote:
True, but we shouldn't go so far as to infer that 1 Hz might sometimes
have more or less than one cycle in a second - no matter how much
different each second might be from the next.

We often infer that a frequency has lessened due to
the red shift which could certainly be a shortening
of a second from the time the light was generated
until now.
--
73, Cecil, http://www.qsl.net/w5dxp