As for Years I would use plain integers instead of Dates because otherwise strange comparison results might show up. If we use integers then you are forced to actualy use a conversion from int to dates and thus are more aware of the incompatibility.

• LocalDate(2018-05-06) > Year(2018)? I would expect no.
• LocalDate(2018-05-06) >= Year(2018)? I would expect yes.

As for the YearMonth, I'm not sure which mapping should be used. I would choose text because it is still orderable and would be the same as MonthDay.

ZoneId and ZoneOffset should be Texts.

For Periods and Durations I'm not sure.

As for OffsetTime I'm not sure whether we should add it at all.