%!demo
%! ## Subtracting two datetimes gives the elapsed time between them as a
%! ## `duration`.
%!
%! datetime (2024, 3, 15) - datetime (2024, 3, 9)
%! datetime (2024, 3, 9, 12, 0, 0) - datetime (2024, 3, 9, 6, 0, 0)

%!demo
%! ## Subtracting a `duration` shifts by a fixed amount, while subtracting a
%! ## `calendarDuration` is calendar-aware — one month before 31 March clamps to
%! ## the last day of February.
%!
%! datetime (2024, 3, 9) - days (3)
%! datetime (2024, 3, 31) - calmonths (1)
