usestd::time::SystemTime;/// A value for specifying a time.
#[derive(Debug)]pubenumSystemTimeSpec{/// A value which always represents the current time, in symbolic form, so
/// that even as time elapses, it continues to represent the current time.
SymbolicNow,/// An absolute time value.
Absolute(SystemTime),}implFrom<SystemTime>forSystemTimeSpec{fnfrom(time: SystemTime)->Self{Self::Absolute(time)}}