resentation, such as
   ephemeris or UTC seconds past J2000.
<P>
 
   For example, a type 1 clock consists of some number of cascading integer
   counters. An individual counter can increment only when the immediately
   preceding counter reaches its maximum expression and ``rolls over.'' Our
   wall clock is an example: the counters are hours, minutes and seconds.
   One tick for a type 1 clock is defined to be the value of the
   least-significant component increment. Clock type 1 uses a
   piecewise-line