Update to the latest version of the spec which was refactored to use
time zone methods record. This requires updating a whole bunch of
callers to pass through a record too.
This also ends up improving exceptions on a missing
getOffsetNanosecondsFor method.
Evidently, going one day forward on the last day of month increases the
month number by one and resets the day to 1. Doing the same on the last
day of the year resets the month to 1.