BenPh[m]: > <@random-task:matrix.org> in a simplified context, a shared, imutable `Clock` is fine. it's a read-only thing, except when tracking overflows, but I think I already have a solution for that.
> 
> The issue is if anything has been missed about reasonable expectations of what implementing a time-counter should imply, and does that include anything that precludes shared **im**mutable state?

But this implies that an `Instant` has some lifetime associated with it. This is a significant thing. What's the concrete type of `Instant<'?>`?