Thanks to Steve Allen, Joseph Myers and Jim Ray for comprehensive answers to my two recent questions.
I wrote: > > ... did > > TAI-UTC vary during the course of a single UTC day? Steve Allen replied: > For practical purposes it still does. See > http://www.boulder.nist.gov/timefreq/pubs/bulletin/nistat1.htm Well yes, though this rather depends on your definition of "practical". There is a significant difference between millisecond level trends in the *definition* of UTC relative to TAI and sub-microsecond level wobbles in particular *implementations* of UTC. For many applications the best available approximation to UTC, from the 1PPS output of a GPS receiver, is at the microsecond level anyway. Ed.
