> I'm not sure if there is an optimization available for the case of the
> two Timespans both having timezone information, but aside from that
> the change looks right to me.

Yes, we should do that since we can.

Chronology-Core-cmm.14.mcz

Chris, I checked out the class comment and even though I thought it
seemed correct, it is probably not the best place to mention that
particular optimization detail.