=begin pod

=TITLE class Instant

    class Instant is Cool does Real { }

An C<Instant> is a particular moment in time measured in atomic seconds, with
fractions. It is not tied to or aware of any epoch.

An C<Instant> can be used to create a L<DateTime> object set to that
C<Instant>. The pseudo-constant C<now> returns the current time as an
C<Instant>.

Basic math is defined for C<Instant>s (as well as L<Duration>s). Adding an
C<Instant> to a C<Duration> returns another Instant. Subtracting two C<Instant>s
will yield a C<Duration>. Adding two C<Instant>s is explicitly disallowed. All
other operations with Instants are undefined.

=end pod
