> The main objective of UTCDateAndTime is to make DateAndTime conceptually
> simpler, but a happy side effect is that it is also significantly faster
> than the old implementation.

Hi Dave, when you first introduced UTCDateAndTime, it was originally
significantly faster than legacy Chronology because legacy had a gross
inefficiency in it.  You work exposed that inefficiency, which was
then fixed, pretty much neutralizing the performance advantage of
UTCDateAndTime, of that time.

If you have made further improvements since then, I would be
interested to see your benchmarks again.

One thing I wondered was, due to greater SmallInteger range, whether
your implementation would be significantly faster in 64-bit image.  In
32-bit though, IIRC, it no longer is..