public enum HebrewMonthNumbering
The numbering system where month 1 is Tishri. This has the advantage of familiarity with other calendars where the first month is 1; it is easier to tell which date comes before which, aside from anything else. It is also the numbering system used by the BCL.
The main disadvantage is that due to leap years effectively "splitting" Adar into Adar I and Adar II, the months after that (Nisan, Iyyar and so on) have month numberings which depend on the year.
The numbering system where month 1 is Nisan. This is the numbering system which matches biblical custom (such as Leviticus 23:5). This has the advantage that the split of Adar is at the end of the numbering system, so all other month names are stable.
The primary disadvantage of this numbering system is that months 1-6 come after months 7-12 (or 13), which is counter-intuitive.