Yeah it's hard for me to get a sense of where that would really matter in practice, or even when it would be correct to do so. You could a `assert!(!span.is_neg

Yeah it's hard for me to get a sense of where that would really matter in practice, or even when it would be correct to do so. You could a `assert!(!span.is_negative());`. Although, you have to be careful, because system time can change arbitrarily. Your watch example is actually an important use case that specifically isn't served by Jiff. You should be using monotonic time (in Rust, that's `std::time::Instant`) for things like that. In that case, you really do get a guarantee that the duration between two instants (one in the past and one in the future) is non-negative. And if it weren't, then that would be worthy of an assert. But you get no such guarantees with system time.