delay until Next;
in time_test2.adb with
  while Ada.Real_Time.Clock < Next loop null;end loop;
cut the time on my machine from 75 to 65 mics.  (The desired Interval
being 57 mics.)
  I tried the same thing using Ada.Calendar instead of Ada.Real_Time.
In ten runs (a total of 100 timings) 89 of the runs gave times averaging
65 mics, while the first timing in each execution of the program, and
the second timing in one execution, gave times ranging between 269 and
428 mics.